Here's a sous vide cooker you can use with any pot for $45.
https://www.amazon.com/My-Sous-Vide-My-101-Immersion/dp/B071...
An ordinary ziploc type bag works fine for sous vide as long as you don't submerge the opening. I've used them for that many times. It's a bit awkward and takes a little more time, but no big deal.