I've have a small Campbell Hausfeld. They're cheap, they work well and are available at WalMart in a variety of sizes.
However, I am surprised to read that you find the on-board compressor to be insufficient! My on-board has a bigger tank and fills faster than my little garage model.
'03 41' Friendship & 24' trailer with HIS '03 H-D Heritage Springer, HER '15 H-D Freewheeler Trike, and '08 Smart Car.
"Adventure is found in the journey, not the destination."