nwoods
Expedition Leader
Right now I don't even have an accessory plug in the rear.
Yes you do. Granted, the wire gauge is not sufficient for much more than running an LED light, but it's there. Follow this tutorial I wrote a few years ago:
http://lr3tips.wordpress.com/2006/05/29/adding-a-rear-dc-outlet-to-the-lr3/
As for the spare firewall access port, Unseenone is correct that it's VERY hard to get to. I found it MUCH easier to poke through the oversized steering column boot, then use existing harness clips to route over to the battery right underneathe the cowl.