I never seen a 12V buffer. If there is one its going to be weak as hell or its going to kill your car battery. Especially for a buffer you need the torque and speed. The problem is if there is one or you do the voltage invertor you'll need a BIG ONE! A buffer draws alot of current so the one out for around $50 won't cut it. If you wanted to go with the invertor you got check whats the max current output (amps) and ask to borrow a friends buffer and check the current draw on the buffer and if the buffer is higher of what the invertor can put out its going to burn out or blow the fuse and also what out for you cigarette lighter fuse also.