Maybe it's switched with the key, or somebody didn't reconnect it. The quick and easy way would be to run 2 conductor cable (speaker wire) and use the same power you are using as a main for the lights. I'm assuming you are not wanting to run the lights with the cigarette lighter power.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)