This place in Tracy rents enclosed car trailers. Here is the link below.
http://www.travlntoys.com/rentals.asp
If you go open trailer do not cover it al all. I covered my boat 1 time in 20 years of towing during a rainstorm. It beat the hell out of it. Fortunately it was Gelcoat and I was able to rub most of the scratches out. From that point on I pull the drain plug and let the rain in if that ever happens again.
Good luck,
Mike