Wrap a belt (preferably with a holster) around the passenger seat. If it's a bench seat, run the belt vertically around the back and modify the holster as needed. Rivets work well. Put your gun in it; it's still OC. You could also mount a holster to the dash top or on a console. If you still think it would not be obvious to a LEO, be sure to mention it when approached.
Don't willingly give it up.