I just got an 8x10 frame from Photo Formulary. It's not luxuriously finished, which is FINE with me. Helps keep cost reasonable, I assume. The back on the 8x10 operates in a much different fashion than I'm used to. It has 4 spring latches on the edge which snap open or shut against the split back. This is different than the normal spring arm that engages the frame presses into the spring back from the center.
Can't comment on how well it works, as I'm only capable of doing 6x6cm contacts right now. But seems fine, if different.