using a very small yet quiet, wait for it… Refrigerator Compressor. Kinda like this. http://www.ebay.com/itm/12V-150W-DC-Tiny-Compressor-for-Air-Conditioner-Micro-Cooling-Refrigeration-/181260257760?hash=item2a33f409e0&item=181260257760&pt=Motors_Automotive_Tools&vxp=mtr
Thoughts?
this one looks the same sort of but it says “Small Volume” http://www.ebay.com/itm/Small-Volume-12V-DC-Tiny-Compressor-for-Air-Conditioner-Refrigerator-/161547760524?hash=item259cff338c&item=161547760524&vxp=mtr
Refrigeration compressors are designed to pump an oil mist out with their air, so you would have to periodically refill it with oil. Similar to how the York compressors do - which is why Oasis had to modify the York that they use to make the oil charge last longer and not get spit out when running.
Copeland used to make a specially designed compressor that was meant for pumping air, and was designed to hold its oil charge and not spit it out. However I am not sure if they still make them. They were very quiet (but required 120v to run as well).
The ones you found on ebay would be VERY slow. You would have to look up the compressor displacement and the calculate how many CFM you could get from it.