Joe and Tom, I very much appreciate your advice and the discussion.
The car does not have a cigarette lighter but it does have a spot on the dash for one. I think just installing a USB charger would be a good substitute rather than installing a lighter and using a plug in USB charger which would require the polarity being reversed somewhere and maybe the risk of possible shorts as Tom mentioned.
I saw the type of USB adaptors that you mention on line and it seemed to me all that was necessary was to reverse the connections as you say. As I have a new wiring harness that has extra wires for an accessory I thought this might be a simple solution. The fact that the USB chargers are plastic and insulated is a bonus.
My remaining concern is the reverse polarity to the USB charger. I am guessing it will not damage the charger, though I don’t know, and what about damaging the phone and its battery? Perhaps this is not a concern with DC current, but being a rank amateur when it comes to electronics I would appreciate your advice.