I can get an oxygen tank, and a regulator, that'll scale down to .12 liters per minute. I'm wondering if you can have people fill oxygen tanks with Co2, i assume if i went to a airgas or something they could. Also is the bubble counter thing needed or is it just cause the other regulars people buy, let it out in psi? If i could get this setup to work, it would only cost me the cost of the co2 fillup.