Most of the newer casebacks will fit (the ones from sport models). I've put a variety in Divers, Rally's, etc. A lot of the sports that Ramon sells have clear backs, and they are cheap, and you end up with a parts movement, hands, and and.... Seiko has been nice of late by making exhibition casebacks in both the common screw in sizes.
If you are looking for snap back cases I think you'll have to make your own.
Well, start making holes I guess hmy: That's about all I can think of. The old Sporto's are lovely, I wouldn't mind have a clear back on one or two myself. The gold screws on the rotor bearing's are too nice to hide (on the ones that have them).