I should let this die but...Other choices are: Reversing ring, they are about $5. and you will have a macro without having to purchase another lens, Bellows, and with adaptors you can get unbelievable captures, Extension tubes, another $5 purchase from China and it will do the same thing as an expensive lens, Teleconverter, yes, remove the lens inside carefully and put it in front of your reversed lens, and my favorite, Drum Roll Please: reverse the final element on a 18 to 55mm zoom lens from concave to convex (or the other way around) and you will get something beautifully unbelievable. Sounds a little wonky but if you want to be different than most give it a try. hear back about Comments please. Cheers.

I hope to one day make a simple diffuser, but when I set about trying to make one, they sort of evolve into a complicated diffuser. But there can be ideas in here that others might find useful.
My flash is the Venus/Laowa dual head flash, which is a strange, expensive, and fully manual flash. The label is KuangRen, but it's really Venus/Laowa (?) I don't understand what the Chinese are up to. Anyway, here is the flash and the current diffuser.
https://live.staticflickr.com/65535/53038103718_bddafd7920_k.jpgParty bowl diffuser, 2.0 by Mark Sturtevant, on Flickr

The bowls are these 7" wide plastic party bowls that are deeply slanted, made by PlasticPro and sold on Amazon. They are set so the short side of the slanted bowls face the lens, and the long sides are to the outside. This is so I can make them sort of wrap around the subject.
https://live.staticflickr.com/65535/53037986395_6233b53e38_k.jpgDiffuser by Marcoli Sturtevantione, on Flickr

But I can turn them in other directions.
https://live.staticflickr.com/65535/53056223591_cc41420475_k.jpgFront by Mark Sturtevant, on Flickr

The bowls have T-shaped openings cut into the base to fit the flash heads and the first couple segments of the stem. Accessory holes are used to strap the heads in with removable zip ties. That's right. There are zip ties that can be un-zipped! Little wood blocks are glued to the flash heads with silicone sealant. This is to keep the heads from rotating.
https://live.staticflickr.com/65535/53056600650_8c8cf9548e_z.jpgBaseDetail2 by Mark Sturtevant, on Flickr
https://live.staticflickr.com/65535/53056224551_273cc08b81_k.jpgBaseDetail by Mark Sturtevant, on Flickr

The interior is lined with silvery HVAC tape.
https://live.staticflickr.com/65535/53056698778_246cc33a10_k.jpgInside1 by Mark Sturtevant, on Flickr

And the diffusing material is 100% nylon trim fabric. This cloth really spreads out the light, but you have to use multiple layers. I use 3 spaced layers. This is the innermost layer...
https://live.staticflickr.com/65535/53056600260_55d3d4cd22_k.jpgInside2 by Mark Sturtevant, on Flickr

The middle layer is attached about halfway out, and the last layer is the front of the flash.

The diffusers are strapped onto the lenses with elastic velcro straps from a CPAP mask. Because of the flexibility of this whole rig, with the bendy arms of the flash and the elastic velcro straps, I can firmly anchor the flash heads in any position to any of my lenses (I use 4 different lenses for different occasions). The 'rivets' holding the velcro straps are brass paper fasteners.
The quote comes from Book 2 of The Lord of the Rings.
https://live.staticflickr.com/65535/53037617226_29e77bdc0a_k.jpgDiffuser by Mark Sturtevant, on Flickr

The are other details, and I will be happy to answer questions.

Here are examples. The 2nd one you've seen before but it shows the reflection of the diffusers.
https://live.staticflickr.com/65535/53055640092_dd55b2ffad_k.jpgLadybugs by Mark Sturtevant, on Flickr
https://live.staticflickr.com/65535/52558022451_57648bfd77_k.jpgBold Jumping spider by Mark Sturtevant, on Flickr

Thank you for looking!

Well as I said earlier I used simple syrup which is nothing more than sugar and water, bees are actually pretty easy to get along with, as long as you are calm they remain calm. Working distance with reversed lenses is not much more than about an inch and a half with a 28mm reversed lens, when using tubes it gets even shorter. When I poured the simple syrup onto the ground soon there were maybe 100 bees massed on that area of ground. For reversed lens work you really need a good flash solution and if you are shooting live bugs a tripod does not work at all.