Just as a follow-up to this suggestion, I also "hardwired" my Bel RX-65 from the outlet in the passenger footwell. I actually modified the Bel's cig lighter plug-in adaptor and then ran the wiring around the footwell to the door seal, up the A-pillar, and underneath the headliner (see below for some pics).
I actually chose this solution so that I didn't have to "mod" any of the vehicle wiring (tap into wires, etc.). Works great and it was pretty easy.
Let me know if you have any questions!
I'm not very savvy at this type of stuff. Can someone help me with where to run the chord to keep it out of the footwell? Thanks.