I have an engine driven air compressor I bought from Air On Board several years ago. It is an air con compressor and came with mounting brackets, a tank, relief valve, pressure switch, hoses, hour meter etc. Everything to do the job. Had to mess with the mounting bracket a little, car is a 4 point tool eater Patrol, and the plastic discharge hose supplied kept splitting. Other than that it is the greatest thing since canned beer. Will literally run all day and with the engine at idle it will pump 33's up from 10lb to 35lb in about 3 minutes. Wind the throttle up to 1200 rpm and look out! And it will run air tools without breaking into a sweat. After 5+ years of pretty heavy use I can't rate it highly enough. It wasn't cheap, $850.00 hard earned but hey it is seriously good. These guys still sell air compressors but not sure they still do the engine driven stuff. Check out their eBay store.
The other accessory I bought a little while ago are some Fyrlytz spotties. Yeah they are old school halogen lights and they use some power, I have the 5000's and the globes are 150 watts each, but any car with a decent alternator can handle them. My car has a 130 amp alternator so no problem there. IMHO they out perform HID and LED lights hands down. Halogen is just such a cleaner, whiter light for.mine. And at $650.00 a pair including a quality harness they are a lot less expensive than "brand name" HID or LED.