The place is called Johnstone Supply. Left off the "e" on the last post.

Check around for an AC supply houses and maybe plumbing (Furgueson, etc) as well.

I have a friend that borrows mine all the time and runs them down all the time. He offered to go fill them and I went along. He is not a welder and was using them for copper pipe (he assumed he had to take them to the AC store I guess, not a welding store). So we took them to Johnstone Supply and they swapped a bottle, pretty sure it was $12 first that trip. A light bulb went off in my head.

Turns out they use a local welding supply I use to fill their bottles too. But with the volume they do, you get great a deal buying from the AC guys over the welding guys. Only works for O/A and probably MC sized tanks, but quite a deal.