Oasis has came out with a new one that uses a 24v compresser at 12 v's 4 wheel mag just did a good article on the set up, but honestly.. thats alot of $$$$
you can buy inverters & wire it in, then get a dewalt or craftsman < or your Fav compressor brand> & run it...
when i was roofing houses in Highschool, we used whats called a biscuit or flat compressor...high output, & a small unit
theres alot of options now days with OBA.... CO2, Engine mounted compressors, Portables
the best question to ask yourself.... how do you want to use it ?
resetting beads on tires? Maybe powertools? or just airing up your tires for street driving after a good day of wheeling?.... Now how quick do i want to wait to air up...20 Mins a tire,15 mins a tire, or have all 4 done in 20 mins & drinking a soda Bs'n with others while there still waiting... or helping them out, drinking a soda & still Bs'n
the reason i'm saying this, the more you want, the more it cost
What are you wanting to run ?