I’d be interested to know where you get the industrial tank too. I read it needs to be food grade.
I wonder why no one has made an open source Soda stream that connects to the big tanks right out of the box in a thoughtful way. Or better yet, a system for refilling the sodastream tanks from a large canister so that the sodastream can still sit easily in your counter.
Not OP, but in my experience you can pretty much always buy food-grade CO2 tanks from homebrewing shops. They usually do refills and exchanges too, as well as selling all the hosing and gaskets and clamps and whatnot you'd need.
You can get Co2 tank and parts from beer supply company.
https://www.morebeer.com/category/co2-tanks-regulators-parts...
plenty YT videos on how to put them together.
https://www.youtube.com/watch?v=7Cb43p5dJBE