I bought a
3 gallon pancake compressor from Harbor Freight. Doesn't take a lot of room. HF has been putting ads with coupons in many magazines lately and this one frequently shows up for $39.99.
I also have a 12v compressor, but it takes a long time to add much air at higher pressures. Works in an emergency, but if I have 120 vac available, the HF compressor is many times faster.