Here is a solution which might be the end all of solutions.
Kase now makes a clip in ND filter(s) that goes right in front of your sensor. Clip in an ND 64, and it will work on every single lens you attach to the camera body.
I might pick up one to see if it is as good as the reviews.

https://www.amazon.com/Kase-Clip-Filter-Dedicated-Camera/dp/B08G8YNPJZ/ref=sr_1_5?dchild=1&keywords=Kase+Clip-in&qid=1615050718&s=electronics&sr=1-5

It should help keep dust off your sensor as well.

Here is a review...

https://www.youtube.com/watch?v=JCUdWWL5jZA

You are asking about a Variable Neutral Density filter. Further, you are trying to cover a somewhat extreme range from 1 stop to 10 stops with a single filter.

I only find one 77mm Variable ND with that range: Vivitar NDX that costs $27. I would bet a filter that cheap isn't very good. It's not multi-coated and the reviews of it aren't encouraging, though some users seem happy with it. Others noted: It softens images... unevenly (need to stop lens down to f/8). It vignettes and gets splotchy at the top end of the range. It doesn't actually have that wide a range and the markings aren't accurate. Folks do like the price and that it fits onto their lens and seems to adjust smoothly.

You want "the best" Variable ND? Look at Singh-Ray. Just be sitting down when you do, because in 77mm size they run from around $400 to well over $500.

Some others from PolarPro, Heliopan and top of the line Hoya cost upwards of $300.

None of those have the range you're looking for. Some of them are actually a pair of filters, each with more moderate ranges, such as a set from PolarPro that cover 2 to 5 stop and 6 to 9 stops. The reason for this is trying to avoid some of the "issues" common with wider ranging Variable ND. One problem is what's called the "iron cross", a large X-shaped shadow the filter causes in the middle of your images. You know how a polarizing filter tends to be uneven on a wide lens when the light source is off to one side or the other? Well, Variable ND are essentially two polarizers stacked on top of each other, so they double that uneven effect.

The sets of two less extreme-range Vari ND are an effort to avoid those problems. But they are expensive, since you're buying two filters, not one. Also the better ones will be more "color neutral", while cheap ones can add horrendous tints to images.

However, no Vari ND is entirely free of problems. Under certain lighting conditions on some lenses they can still have some uneven effect or add a tint.

Buy where you want, but for reference B&H Photo stocks a lot (25) of the available brands and they show choice of 43 different Viable ND filters (or sets) in 77mm size: https://www.bhphotovideo.com/c/search?q=variable%20neutral%20density%20%28nd%29%20filters&sort=PRICE_HIGH_TO_LOW&filters=fct_circular-sizes_27%3A77mm

I don't see these on B&H website, but a "cheap" brand of filters I've been experimenting with are "K&F Concepts". Made in China, their top-of-the-line are "nano" multi-coated and use German Schott glass, same as B+W and other premium quality filters. So far I've only gotten their CPLs in a couple sizes, but was considering trying some of their fixed strength ND (not variables). They do offer a lower grade, wider ranging Vari ND. But like some of the major brands above, K&F also offer a pair of higher quality filters, each with smaller range that they claim avoid the dreaded X-shaped pattern in images.

1-stop to 5-stop: https://www.kentfaith.com/lens-filters/nd-filters/nd2-nd32-filter/KF01.1063_77mm-nd2-nd32-variable-nd-filter-18-layer-multi-coated-glass

3-stop to 8-stop: https://www.kentfaith.com/lens-filters/nd-filters/nd8-nd128-filter/KF01.1079_77mm-nd8-nd128-variable-neutral-density-nd-filter-nano-coated

Again, I haven't tried these particular filters and can't say how well they work. I just got the two of K&F's circular polarizers in a couple sizes and haven't shot much with them yet. They are the same series as the above Vari ND filters and these CPLs seem really good quality for the money... While the specs are similar, I can't guarantee the Variable NDs.

Another possibility... Are you shooting stills or video?

Video has less available in-camera exposure adjustment and can require a lot of different strengths of filtration. As a result videographers who don't want to have to buy a whole bunch of different fixed-strength ND filters might want a Variable ND - like those listed above - and just live with any filter shortcomings.

However, if you're just shooting stills, there might be a better solution. Buy one or two standard ND instead (i.e., non-variable). With still photography you have lots of other exposure adjustments available in-camera, so really don't need a variable filter. Instead you might consider getting just one, such as a 6-stop or 8-stop. Or, maybe two such as a 3-stop and a 6-stop filter.... then you have two different strengths as well as option to stack the two filters for even stronger effect (so long as there's not a problem with vignetting on a lens).

This is what I plan to do, since I don't shoot video. I won't be able to buy fixed strength K&F brand, though. They don't appear to have them available except in kits with filters I don't need or want and not in the strengths I want. Other affordable brands that appear to be good quality and multi-coated include Gobe (now Urth), Haida and Formatt-Hitech. The top manufacturers make fixed strength ND, too.... but they are pretty expensive. A pair of Hoya or B+W or Heliopan or Breakthrough Photograpywill cost $250 to $300_ in 77mm size. Note: Some brands, such as Hoya and B+W, offer different quality filters at a range of prices... There are cheap uncoated Hoya as well as high-end, nano multi-coated versions, and often several grades in between. B+W uses top quality Schott glass and brass frames in all their filters, but offers SC single coated that are okay indoors, very good quality F-Pro (or MRC) that are 8-layer multi-coated and top-of-the-line XS-Pro that are 16-layer "nano" multi-coated for oil/water/scratch resistant and use "slim" frames.

Here's a list of the multi-coated 77mm size ND filters B&H stocks in the 3-stop and 6-stop strengths. https://www.bhphotovideo.com/c/products/Neutral-Density/ci/114/N/4026728350?sort=PRICE_LOW_TO_HIGH&filters=fct_circular-sizes_27%3A72mm%2Cfct_density_2336%3A0.9-3-stops-8x%7C1.8-6-stops-64x%2Cfct_features_2339%3Amulti-coated%2Cfct_nd-combinations_2338%3Astandard-nds There are other strengths, if you prefer. And, other places like Adorama, Amazon, etc. stock them too in a wide variety of brands and strengths.

Another good source of filters is: https://www.2filter.com/

FYI, neutral density filter designations can be confusing. In case you don't know:

0.3 and ND2 are 1-stop
0.6 and ND4 are 2-stop
0.9 and ND8 are 3-stop
1.2 and ND16 are 4-stop
1.5 and ND32 are 5-stop
1.8 and ND64 are 6-stop
2.1 and ND128.... 7-stop
2.4 and ND256.... 8-stop
ND400 is approx. 8.5-stop
2.7 and ND512.... 9-stop
3.0 and ND1000... 10-stop
Yes they round the above to 1000 instead of 1024.
... and there are some even stronger ones.

amfoto1 has brought up some good points. I am getting ready to get neutral density filters. My findings from in the pass film days is that a cheap filter is just that - a cheap filter. After my first two cheap filters I never bought another. Sometimes the cheap equipment and accessories will do just as well as the the expensive. No need to spend my hard earned money on expensive items when cheap items do just as well. But I have not found filters to be in that category.

The information that I have found about variable NDs (reviews, opinions, etc.) indicates my money will be better spent on simple NDs, not variables. If I can save my money and have some patience, the best multi-coated, nano finished filter will be purchased. I have never been been disappointed by my filters after those first two. They are expensive but I promise you they are worth it in my opinion.

My plan is to first buy 3 stop NDs in all filter sizes for my lenses. Next will be 6 stop and then 9 stop NDs in all my sizes. Size and cost wise this is big and expensive. But in my opinion, the quality is worth the cost and hassle. If the 3 stop NDs cover a majority of my ND needs, I will place the other NDs further down my "to buy" list. Also, the filters I will consider buying will be B+W, Hoya, and Breakthrough with the emphasis on quality first and cost second. I will consider other possible filters if they can match those three manufacturer's quality and have a lower price.

I have a couple of B&W, lots of Hoya, and one Heliopan - they are all good. All have casts, but all are optically flat and well-coated, not contributing distortion or flare. I hear good things about Breakthrough filters (glass by Schott, which is owned by Zeiss) but my needs are well-served with what I have. Hoya owns Pentax, Kenko and Tokina, and makes all sorts of glass for sporting, scientific, video and film and industrial purposes, and B&W is a Schneider-Kreuznach, which was established in Germany in 1947 - and similarly has a great reputation in multiple industries. I have never had good results with Tiffen, Quantaray and other junk. A color cast is not a reason to dismiss a filter - almost all filters have them.

After 55 yrs in the industry, I have come to understand that price does not necessarily predict optical quality. No point in spending $150 or more when a $40 Hoya HMC ND will provide similar results. Shooting raw will make it easy to resolve color cast issues.

https://www.the-digital-picture.com/Reviews/10-Stop-Neutral-Density-Filter.aspx

https://fstoppers.com/gear/neutral-density-filters-compared-it-ok-go-cheap-345214

https://www.theschoolofphotography.com/tutorials/10-stop-nd-filters

https://www.diyphotography.net/cheap-nd-filters-really-good/

Here is a solution which might be the end all of solutions.
Kase now makes a clip in ND filter(s) that goes right in front of your sensor. Clip in an ND 64, and it will work on every single lens you attach to the camera body.
I might pick up one to see if it is as good as the reviews.

https://www.amazon.com/Kase-Clip-Filter-Dedicated-Camera/dp/B08G8YNPJZ/ref=sr_1_5?dchild=1&keywords=Kase+Clip-in&qid=1615050718&s=electronics&sr=1-5

It should help keep dust off your sensor as well.

Here is a review...

https://www.youtube.com/watch?v=JCUdWWL5jZA