Pickings are slim for the 2x C3M set-up, being an almost exclusively Combine thing from what I can find. The DCMS Tai-Sho carries x2 C3M as does the Kuritan-variant CM model of BattleMaster, as does the Naginata C3B.
Best bet otherwise would be the Cyclops C2, which first came out in 3073 per the MUL as an IS General design.