All the way down to $50 at a few places on the net is the once pricey GGS Hoodeye HD DSLR LCD Flip Viewfinder. Made by GGS out of China but sold under several brand names like Perfect and Neewer.
The GGS Hoodeye VF is labelled as foldable but really is just a flip Viewfinder with 3X magnification and 1:1 when the eye cup is flipped. The GGS VF is suitable for cameras with 3″ LCD screens with a ratio of 4:3, and is compatible for LCD’s with a ratio of 3:2.
The Viewfinder has a +3 diopter for the short or long sighted shooters.
Check out Jonathan Nicol’s review of the Perfect Hoodeye Viewfinder:
See GGS for more details.