lowes used to sell a kit to do this. IIRC, it just used regular paintball tanks and adapter fittings. you could do this yourself as used paintball tanks are cheap as kids get into it then out of it and ditch the equipment at yard sales all the time... I've got over 20 of them in various sizes.
Also, they make similar sized air tanks just for paintball They need to be filled at dive shops or paintball shops with special compressors, but hold like 3500-4500 psi of air. Advantage is they don't freeze in sub 40 degree weather as CO2 will.
fittings are available as well as bulk fill kits if you already have a big co2 tank. in my case I have a couple old soda machine tanks I bulk fill off of...
unless you are into paintball and/or already have the equipment, it would probably be cheaper in the long run to just go electric.