Check out this link,
http://www.onboardair.com/ There are a number of options, this one in particular is a great company, you can buy a portable "air bottle" and fittings or the components to provide "OBA" or on board air that will not only supply air for your tires, but air tools as well. If you check out the 4x4 supply company sites (about eighty-gabillion), you'll also find units that will operate electrically and provide a sufficient amount of air to "air-up" in a reasonable amount of time.
Good luck,
Mark
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