You'll wanna get stainless steel and try to find one with a nice thick or layered thermal diffusing bottom that will spred the heat evenly.
I got mine from a Macro teacher and it's a beaut. I've had it at least 15 years an it'still like new. It's made in Italy and the brand is Aeternum. They're not cheap but it'll last a lifetime.
I believe I paid around $75 bucks back when. I've seen them around on the net so do a search with the brand and "pressure cooker" as your search criteria and I'm sure you'll find them.