I don't recall TNC ever making C series bodies, just extensions and adapters. They make a bare 18650 body for their SF series, but I don't think that can be adapted to work with a C series head/bezel.
Maybe there's a compatible 6P clone from DX or KD that accepts and 18650 and is available in bare Al or could be easily stripped?
I don't know if Lighthound ever carried a bare Leef body (it's not currently listed). They do list one of the bare Leef E head/C tail 18650 bodies in stock, but I don't know if anyone makes a bare E2C adapter.
You could also strip and bore a 6P body. I don't know if they're still available, but GenEric808 offered some stripped 6Ps at one point, and there are a few members offering boring services.