I ended up reaching out to Rivet and Hide, and they had one size large left that was just a smidge over 22" in the chest, right on the money for what I'm seeking in my next type III (A jacket I can wear over sweatshirts and flannels...my olive whipcord type III fits wonderful, but it is more tailored through the body).
The sleeves are a smidge longer than what I am used to at 26.5" long, but I imagine the creasing on a 21oz type III will bring them in a bit over time.
I have to give a shout out to Rivet and Hide for their great service, right up there with the Iron Heart crew!