My favorite 10X triplet loupe donated its lens to this cause. I used a 28 to 37mm step-up adapter to attach it to the camera. The threaded adapter is just a snug 'snap fit' over the body. The lens opening was bored to the lens diameter + .001". I used Kodak black paint inside too -don't really know it is necessary. The lens is just held in by a Delrin ™ ring - painted black. It is a light snap-in fit too. These snap fits make disassembly easy while in the formative stages.

I'm finding out that I want to move the lens even closer to the camera lens. Right now the loupe lens is .150" from the Nikon's lens. I want to get it about .100" closer. More work with the boring tool.

Greatest magnification is with the lens about 3/16" from the photo target. At this point, it starts cutting off all light. Need more thinking here. Still a work in progress - of course. Hmmm.

I do have a 16X doublet loupe that isn't used around the shop. Too powerful.