You'd need a BIG inverter, and a heavy-duty battery and alternator to support it! Why not just install a second evaporator on the existing engine-driven AC system? I'm doing that on a motorhome I'm restoring, using a factory rear AC evaporator out of a conversion van somebody gave me to get it out of their back yard. It's a little work, but all the parts are useable, with a little tinkering.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!