Cut the back off the cigarette lighter housing and get a marine-type pushbutton starter switch. Solder or braze the nut that attaches the switch to the back of the lighter housing, and adjust it in or out until pushing the lighter in operates the switch. Use a second nut to lock the switch into position. If you want to, use a drop of Super Glue to attach the lighter permanently to the pushbutton, or just put the lighter in your pocket when you park the truck as a handy anti-theft device.
Jerry