Try using an advanced search. Or do a google search for aquarium co2 system. Rex's stuff is great
First you need a CO2 based fire extinguisher. The chemical ones will not work.
Be careful with that! When you get a CO2 cylinder refilled at a welding supply house or someplace that deals with beverage equipment it's usually lab grade stuff, or very close to it. A paint ball store/fire extinguisher service may not have the purity levels we would like to have. There may also be other gases mixed in, albeit at very low volumes....in Seguin, there is a very nice fire extinguisher place that will fill your CO tank for fire or for paint ball, they thought I was nuts or doing something illegal until I brought in pictures of my tanks. Nice people. Shop is on Austin St. if anyone is looking for c02 fills in south Texas