I use this one and it has been good so far, but then like healthservices said I am only adding a few lbs here and there. Mostly I am letting out at the track when they get really hot, and if there is a tank (and there usually is) I use that to fill back up before going home. I mostly use it at autocross when there is no tank available.
Amazon.com: Viair 00073 70P Heavy Duty Portable Compressor: Automotive