why cant you just go to a Junkyard and gank the unit out of a Beamer or a Lincoln? just go in, pull the unit, pocket it, and grab a switch so the guy doesnt think something is fishy, he'll probally give you the switch because, common, its a switch.
wire that badboy up, and BAM, there you go.
although what about a trickle cellphone charger? pull out the guts and wire them up and link a Capacator infront of it, and then once the wire goes cold, the capacator will discharge and the charger will slowly drop the charge to the lights. would that work?