how about using an inspection sticker mount for a motorcycle? I bought one for my motorcycle. didn't want to stick anything to my bike so got one of those. it mounts to one of the four corner bolts that hold you license plate on then you put your sticker on the bracket. Nothing is permenant. ebay motorcycle inspection sticker plate.
MILITARY BASE OR MOTORCYCLE INSPECTION STICKER PLATE - Aluminum 3" x 4" | eBay