A inexpensive alternative is to purchase an enlarging lens and extension tube or bellows to mount.

I have had success with a Schneider makro apo componon, which is very similar in build with their enlarger lenses, which is on an adapter which allows micro focusing, as well as a set of m42 extension tubes, with a m42-Nikon adapter.

I have taken pictures of the pores on my finger tips with it. Razor sharp.

A ring flash would be optimal but I use a simple corded setup off camera.