A friend recently got a portable compressor rig:
Amazon.com: YF youfu Cordless Airbrush Kit with Compressor, 32PSI Handheld Mini Air Brush Gun Set, Portable High Pressure Air Brushes for Painting, Tattoo, Nail Art, Mode, Makeup, Cake, Barber : Beauty & Personal Care
Or you could try this:
Is THIS the FUTURE of Mini Painting?! - YouTube
You don't want to go the spare tire route! I used to do that, and remembered needing to re-inflate every 30 minutes or so. I used a full sized tire, so the tiny space-saver tires in cars these days will have you working out!