Circa 2007, Toy Soldier ( it's a brand) released an exclusive Vietnam figure - Kenn Miller
He was a shorter body type. Somewhere in the 9-10 inches range. How easy to find today? No clue.
What I would do, in your shoes, is to try to find a Dragon Models female figure, convert it to use a male headsculpt, pad the inside a little to fill out the figure a bit for depth ( you could literally use cotton stuffing and duct tape here) and add some reworked male clothing onto the figure.
Just some thoughts. Good luck.