How about slapping it on the inside of the passenger side of the windshield. I see folks around here do that sort of thing all the time. Down low on the far right and if you are worried about it falling down use a piece of clear packing tape along the top and side.
Just my 2 cents.
Brad
I did that for a week before a trooper pulled me over, there wasnt any factory license plate mount on my Sidekick, so I just used 2 drywall screws into the bumper cover right in front of the trooper, he wasnt impressed and still wrote me the ticket, I told the trooper no problems, that i was going to the judges house directly and have him dismiss it. I dont think he actually thought I was going there, but he followed me and was very pissed when the judge told the trooper to stop being an ass about such crap and to look for actual criminals.
Currently i have the plate centered on the bumper cover, but I have a 120w LED light bar coming and it will be mounted exactly where I have the plate now, so i will mount the plate to the upper horizontal portion of the bull/push bar from the backside.