I have this set up on my 24v...with a little work you might be able to make one of these York compressors fit a 12v.
It does work great. I got my compressor off of a 79 Dodge van for $10 from a junk yard and the thing is still going strong 5 years later. I have a 7 gallon air tank and with the truck at idle it will keep up with my 1/2" IR impact gun pretty easily.