I've got a home-grown CO2 setup that I'll be putting up for sale sometime in the not-too-distant future. 10lb tank (it's even painted Expedition Green!), dual-gauge regulator (tank pressure isn't entirely worthless, as it'll give you an idea of what the temperature of the tank is, with the tank warm, it'll read about 1000psi, with it cold, i.e. after a fresh fill, or after a lot of hard use, it'll read about 500psi.) Fully adjustable. Comes with regulator and tank. Hose and fittings not included, but you can get a hose & fittings kit for about $15-20 at Sears for a good one, or about $10 at Harbor Freight for a crummy one.
Takes about 30-40 seconds to fill my 32s from 16 to 42psi.
Tank will be shipped empty. $120+s/h.
The old, red, tank is pictured. Regulator is the same. I'm upgrading to a 15lb tank, and installing a compressor based OBA.