I have an AE finder. What I need is the magnifier that attaches to the eyepiece. It's quite helpful in macro/closeup work. Thanks for the link however.
What you are looking for is the Canon Magnifier R + S Adapter. It was made for the F1 and F1n but may fit the F1N as well as the A series Canons. If you are doing serious macro work the Waist-Levei Finder FN-6X is the best
I'll add, assuming this is about the New F1, last model, that Finder FN-6X is a must (or big time help) for macro work. I do not like magnifier so much, only 2.5 X magnification, not the same at all (or even remotely similar) as the Finder FN-6X, which stands for 6 times up.
Make sure you get complete set, often you will find bits and pieces. Magnifier R was sold alone, adapter R also (as was S). Sometimes you will see adapter flip up frame but nothing else on it (just plain metal section), and there are pieces that allow the whole thing to actually mount on the eye piece.