I tried all the industrial gas places in my town and only found one that would sell a 20lbs or less co2 tank, for private use. I got ripped off by them too. I found out shortly after I bought the 5lbs tank, that I could buy a 20lbs tank from the hydroponic shop for almost half the price

.
I bought the Milwaukee regulator, solenoid, bubble-counter and needle-valve set-up off e-bay and it works. I use the DIY gravel vacuum reactor.