I found Bass Pro Shops had some great deals on large SS pots. Restaurant supply stores are another good source. I didn't have much luck on Craigslist, but I was in a hurry to get it and didn't have the patience to check for a few weeks to see if one would pop up.
this is what using right now. i dont know a bout shipping cost theres a store right from my house. but it seems to be a nice heavy pot. its shiny and stainless anyways.
I really stand by Austin Home Brew... they have great service and have great products... Their SS line of pots are pretty affordable and they are great quality. The other option in order to get a good sized SS brew pot for cheap is to get a Keg and cut the top off of it...
Find a stainless steel keg on Craigslist, often you will find them for free. Take it to your nearest high-school metal shop and have the lid cut open and a hole drilled at the bottom.