I own the Cavision Micro finder and I have found it to be pretty accurate for Super 16mm, 1/2" and 1/3" video as well as some 35mm. I got it because it was the best deal, $200US from B&H (link below), but have had absolutely no complaints with it. Only thing might be that the viewing area is a lot smaller than say a Mark V, but that's the price difference. Every director I have worked with loves the finder immediately.
http://www.bhphotovideo.com/c/product/1842..._.html#features