I get contact prints of my 220 rolls done at a local lab (Icon in LA). They use 10x12" paper. I have not found a way to store the contact prints so they stay in consistent order with my negatives. Are there special binders or boxes that I can use without having to trim the sheets? I've got about 2000 sheets piled up in a box, so if there was an easy way to file these, I'd appreciate the advice.

You can get A3 sized "4 ring" folders (the wife brought some home from work they were chucking out) that would hold them.