That's a cool site DaveO. When searching cl I usually have the best luck looking for "torch" or "acetylene" as key words rather than "welding bottle".
I paid exactly 0$ for my last 350cf bottle. A neighbor had an old bottle he used in his truck to run air tools when he was out on his farm, but upgraded to a portable air compressor and I got the old bottle. My Lws took it and gave me an argon cylinder with no charge other than the fill up (95$).