The C-A1 and S-A1 series have the same barrel lengths, 3.6" for 9mm and 3.8" for .40 S&W. The difference is that the S has a shorter grip. Since grip length is usually irrelevant to holster fitment, I assume that both pistols will almost universally fit in the same holsters.
FWIW the M-A1 and L-A1 series have longer barrels, 4.0" and 4.6" respectively.