Kind of depends if you want a Fixed A-1 stock which are shorter than a fixed A-2 stock. The easiest route would be to buy a complete A-2 stock like the one from RRA or White Oak Armory.
Brownell’s sell fixed A-1 stocks and you can call Brownell’s technical to see if your commercial buffer tube will work with a particular stock.
I checked but Brownell’s was out of stock but Midway has a couple of options. I’m sure other vendors still sell A-1 and A-2 fixed stocks, if nothing else for people wanting to build a retro rifle like an M-16 A1 or A4.