I'd just get 58mm filters. Sounds like that would fit your lens. You might get away with using the smaller filters. The thing to check is how big is the front element. I have a nikon that I swear the filter ring is twice the size of the glass. Try it and see. Only way to know for sure.

One other thing is to watch ebay for the sort of filter holder that is in the Simmons book. Something like this one.


Takes 3x3 filters. Personally I get the feeling just using screw in filters is easier but if you've got multiple lens with different sizes.