I've heard great things about the Versalab as well, but I went the cheap route - 2 mirrors and a prism from an old pair of binoculars. One mirror sits on the baseboard or easel, or held against the bottom of the lens. On the second, I scratched a small circle out of the plating. This one goes in where the negative holder normally sits. The reflective sides face each other. The prism sits on the top mirror and allows me to look straight ahead and down through the hole. If everything is aligned, you get that endless barber-shop effect.