Power Tank too expensive, I like the CO2 idea. Goto Ebay, get a 10 or 20# aluminium CO2 cylinder, for under $100, $30 Habor Freight CO2 Regulator, $10 Habor freight hose and fittings. Should cost you less than $150 and you get the same thing as a power tank.
Another option, get a 1000 watt 12vdc/AC converter $60-100, $80 Habor freight 2hp 2gal AC compressor. Use it on the trail or at home. May be bulkly, but it has everything you need, 115 psi and all the switches. YOu could probably pull it apart and hard mount it to fit better, too.
The standard is two 12v compressors tied in with a tank.
Then of course the York, powered off the engine.
There are others and variations there of, right now I'm trying to decide on a rear locker. I want to go ARB, but It's still quite expensive, I have a line on one, but I will not know until Sunday.