Really Tony?
I got mine from Air Liquide and I think I own mine. Every few years I exchange it for a full one for around $40.

Mitch

This would have been about .... 1 - 1/2 years ago ... maybe they've changed now, but I got a real runaround back then when I called all of the big CO2 places trying to buy a cylinder. Renting/leasing would have been easy enough but owning the cylinder seemed to be a real foreign concept for some reason. Maybe things are different again today, ... I don't know. There was one place that would sell me one, but it was an odd size, like 7lbs or something. Anything from 2-7 lbs (or whatever it was) would have been OK but anything 10lbs and up they wanted me to lease it.

I should mention I only use Sprouse for the testing and fills. They don't sell the cylinders either but they'll at least work on them if you show up with one. I ended up buying my cylinders but it's all aquarist-to-aquarist dealings.