I picked up a filled 20# co2 bottle with brand new regulator off of a local board for $100. Works great, the only downfall is it is not a "high flow" regulator like the power tank so it will frost up if you try running power tools for an extended period of time.
You can wrap heater wire (12v), found in heated seats, around the reg. Hook it up to a 12 volt outlet. Worked for me with my #20 (who is now living life charging homebrew kegs).
