When I first used an airbrush, we rented industrie air bottles. I think they were 100 liter and preasure 150 Atm. that's 15 cubic meter air, Il'l let you calculate, but an interesting calculation would be, how many minutes a small compressor shal run to move 15 Cubic meter air.
Or, if you know how many liter air your airbrush use pr. minute and calculate that up to the 15000 liter Air that can be in a 100 liter or 150 liter industrie air tank.
I think it will be a surprise, how much time.
CO2 are used in fire extinguisher, on Ebay a CO2 or an air preasure valve don't need to be that expensive, an old oxygen valve are not different, it's the same except the tread to what bottle ;oxygen, CO2, Air, only difference are the treads in the valve and that piece, the nut and the small pipe can be replaced.
CO2 don't need to be that expensive a solution, bottle and valve can be bought second hand. But if you are uncirtain of that, you can do as I d´just did but also that is a chance, --- see the tread I made about my new compressor, I bought a Vintage dentist compressor, beecaurse it is allmost silent, -- when I put a reduction valve on it I will know if that is the right .