South Vietnam seems to have gotten most if not all of their uniforms from the United States.If you were to use American Vietnam War era figures and add Asian heads you should be fine.

Sadly there are hardly any ARVN options. Some time back I sent Bravo6 an email asking if he would make some ARVN troops (infantry and armour), but there was no immediate plan.

You can get away with using the figures from the Academy M48A5 kit for ARVN tankers. Their helmets aren't 100% correct though, but figure size and facial features are perfect imo). Otherwise there isn't much.

ARVN uniforms also tended to have less baggy trousers than US ones. There are some Tamiya figures with that sort of cut but you’d need to do quite a bit of surgery to get the build appropriate and to adjust the uniform details and obviously add new heads. On the plus side, nobody else will have figures exactly like yours....

While I’d also like to see someone like Paracel or Bravo 6 do some ARVN figures, I suspect that the chances aren’t great, particularly I suspect in the case of Paracel. The ARVN is effectively being erased from history in VN (cemeteries are neglected, contrary to how even those who fell in the service of Nazi Germany are treated in some of their victims) and therefore awareness is low and not encouraged. Sad, given that they were fighting to defend their country in the same way as many others but they had the misfortune to be on the wrong side when it was over.

And if you’re trying to make a profit, there may not be enough demand to make them feasible. At least we can get some decent PAVN figures now, not that it helps you.