About 12 years ago, a couple manufacturers thought there might be a market for 2-rail TMCC. Atlas offered several models in 2-rail TMCC: RS-1, SW9, GP60, Erie built. Weaver offered a couple models: USRA light pacific, VO1000. This was all roughly 2004-2006.
Then it just all dried up, clearly not enough sales to justify continued production. Although several of us argued that it would be no trouble for manufacturers to install TMCC in a few locos since they were already putting TMCC in 3-rail units.
Nowadays those wanting 2-rail TMCC have a few options. Pick up these units as they appear on the secondary market; install TMCC in 2-rail models (rather than install DCC); convert 3-rail TMCC locos to 2-rail.