Easy killers, the only reason to fill your tires with nitrogen is as mentioned above, because it stays in the tires longer (NOT because it is lighter lol). either way, its a rip off. Back to the subject, when I mentioned a small compressor, i meant like a 5 gallon tank or something like this:
Amazon.com: Porter-Cable C2002-WK Oil-Free UMC Pancake Compressor with 13-Piece Accessory Kit: Home Improvement