Another vote for a small, portable air compressor that runs on 115V regular house current. Get that, get one with an integral regulator or get a pressure regulator to put on it, probably less than $200 out the door, but it will last your lifetime, you will definitely wonder what you did without it. Get a blow gun as well, wonderful for cleaning out fans, etc. that build up dust.
Sears and Northern Hydraulic are just 2 places you can get a new one, from time to time pawn shops have used ones, even Goodwill etc. occasionally have them.