The 7/8" full split (two-piece) rings required for an M84/M1903A4 are getting hard to find. A GI set will probably run $250.
I haven't seen a Griffin and Howe mount for an M1C for sale separately for awhile. Given what the rifles are going for I would Imagine they are at least as expensive as an M84.
Good luck!.. Keep an eye open at the shows and WTB lists.