Just put a copy of the bill of sale in the back window
Seriously.
I sold a H1 hummer to a guy from Michigan. He and his family flew down and I picked him up at the airport. Took him to the truck, and they loaded all their luggage into the truck. I asked him if he had a plate and he said nope. I'll just put a copy of the bill of sale we sign in the back window and drive home. He said he's done it many many times with no hassle.
