If it is just for LED lights (don't know why I didn't catch that originally, guess I was going by the thread title?), buy a Luminoodle or a knock-off on amazon (I have a couple of color strands), kits come with their own power cell or will run off USB, some with remotes, other change colors, 5 feet to 25 feet. you can get them from $15-70+.
There was just a small Luminoodle group buy, I bet it enough people showed interest he would start up another, he started a list.
Can't reiterate enough, should still carry a dedicated jump pack regardless of what you choose. Too much bourbon and music... forgetting to turn off your key before passing out... nothing better than a car camp hang over and no way to get to the small town diner/cafe for a big cholesterol bomb breakfast