Would have been nice if there was an easier way to do this...my wife just asked me the same question about her new Mazda5. With her last car (Chrysler Town & Country) I just unplugged a relay and plugged in a bypass (available at the dealer for around $5 IIRC)
I would expect there is a constant 12v source at the radio/head unit. You could reroute your cig lighter to that. I would have to double check schematics and wire sizes to insure a margin of safety.
To be safe, you need to isolate the outlet.
Put a diode in series with the 12volts going to the outlet. Then feed your constant 12volts to the 'load side' of the diode. This way, 12volts cannot 'go back' to whatever ciruits needed to be off.. when engine is off.
-- come to think of it, there is a fuse for the outlets in FO2 (second fuse box).. you can rig a 'fuse + diode' box, and then feed your constant 12volts.. at that location.
(rofl)Then again the kit is to wire it into a switched source, don't want some kid in the third row getting shocked and piss his pants! LOL! (shocked)
Peace!(rei)