I use a Sekonic L358 meter. It's a discontinued model, but the L308 is functionally very similar. The main difference is the L358 can be fitted with modular, internal radio triggers to work with some specific systems (I have the Pocket Wizard and Radio Popper modules), while the L308 cannot. Not a very big deal because if you wish you use the L308 or most any other meter in conjunction with an external radio transmitter to serve the same purpose.
Flash meters are "incidence" meters. This means they measure the light falling
onto the subject, which can be a more accurate way of setting exposure. You point the meter at the light source to take readings. With multi-light setups, it can be used to test individual light output to establish ratios, as well as measure the the combined output of the lights firing as a group.
I carry my L358 most of the time. They work just as well with ambient light, indoors or out, as they do with studio lighting and flash.
Cameras' internal metering systems are "reflective". They measure the light being reflected back at them
off of the subject and the rest of the scene in front of you. As a result, camera metering systems are highly influenced by the tonalities of the subject and the scene. This is why cameras have Exposure Compensation that allow the user to override the metering system and make corrections when shooting with the auto exposure modes. Exposure Compensation is not necessary with incidence meters, since it measures the light source and aren't influenced by the reflectivity of the subject.
Sekonic meters are good. They make a variety at different price points, with more or less features. I'm happy with a fairly simple one like the L358/308 that handles flash and ambient incident readings. Some also have reflective spot meters, but I've already got that in my cameras, as well as have a Pentax 1 degree spot meter.... don't really need another. Some of the Sekonic are still designed to work with very specific radio triggers, but AFAIK are no longer interchangeable.
Gossen and Kenko also makes some excellent meters. I've used Gossen in the past... As well as Minolta, which are what Kenko are based upon (Sony bought the entire photography division of Konica-Minolta in 2006 and immediately turned around and sold the metering system to Kenko).
A couple things to look for....
If you plan to travel a lot it might be good to look for a meter that uses a really commonly available battery such as a AAA alkaline. Some use rather obscure batteries that can be hard to find in an emergency.
If you buy used be a little careful. The reason I replaced my older Minolta flash meters was because they were more appropriate for film than for digital. They don't have the ISO range and shutter speeds needed for modern digital. It's possible that some even just a few years old may not have some of the ultra fast shutter speeds or ultra high ISOs found now on the very latest cameras. These things are only noticeable at the extreme settings and can be worked around pretty easily.
While I have some vintage ones in my collection, one of the oldest meters I still use at times is a Sekonic L298 Studio... which actually isn't a flash meter. It's an incidence meter, but only ambient light. It requires no battery at all, has an analog scale and is perfectly accurate even after 35 or 40 years. But, again, it's not a flash meter so wouldn't be what you want. I think the modern version of that is an L398, that's also not a flash meter.
B&H Photo appears to offer eighteen different flash meters. I'm not familiar with all the brands.
https://www.bhphotovideo.com/c/products/Lightmeters-Accessories/ci/900/N/4077634543?filters=fct_lightmeter-type_1792%3Aflash