Easier and cheaper DIY option for a "22 would likely be cutting down a 55 gal barrel. They typically go for 20$ or so around me and are the same diameter, depending on where you cut (ridges or not). There are probably a few threads on here where others have done it already. Only thing to look out for is what was previously stored in them / any liners. Usually a good burn or grind will take care of it. I have a guy who has a bunch that used to hold isopropyl and lets em go cheap.
Probably cheaper and easier for DIY than finding a 22" stainless stock pot.
If wanting to go the stock pot route, I'd look into the sizes of some of the Turkey Fryer / Crab / Cajun boil pots that are sold by companies like Cajun Bayou etc. They have some pretty massive pots.