Consider a Canon Angle Finder B, 2nd-hand. More robust than the Angle Finder C, smaller, and undoubtedly cheaper. All you lose is the magnification switch from 1.25x to 2.5x. If that doesn't matter, the 'B' is a good option. I own both, and I prefer using the 'B' to the 'C'.
There is also the 'A', but that's older, likely rarer, and the image is left-right reversed in that one -- so all the stuff at the bottom of the viewfinder will be reversed as well---perhaps not so good for DSLRs...