This isn't a solution that will work for everyone, but as an avid SCUBA diver I've usually got a couple of SCUBA tanks in the garage that I need to have refilled. They're 'empty' for purposes of making another dive, but will generally have 500 to 1000 psi left in them. The regulator steps that down to about 130 psi, and with a tire fill adapter plugged into the BC inflator hose, you can fill a lot of tires with compressed air that would otherwise go to waste. I've also got a 5 gallon portable air tank, that I'll fill from a SCUBA tank when I want something lighter to carry around.
I do only use the air tanks for this, not the high-O2 nitrox mixes.