I wonder if you could just go thrift store shopping, and buy up every old stove top pressure cooker you could find (like 20 of them, for a few dollars a piece), and then hook them all up to one steam boiler. I'm sure that could be reverse engineered from something, or made on a budget too.
Like, tap into the lids and add a line going to each one, to pump in the steam to all of them at the same time.
Sounds more reasonable to me, instead of paying 1000's of dollars for a large commercial unit with a single huge pressure tank, or trying to engineer one that won't blow up.
Then you could cook 20 times the amount you could with just one regular sized PC, without breaking the bank to do it, granted you have space to hook it all up.