I hear about (and am considering for my son's car when he is traveling) one of those bubbles that are filled with air from a blower. Sort of like those temporary buildings (and some semi-permanent). What I like about them is; a) you can get them pretty tight so rodents can't enter and; 2) because of the constant movement of air trapped moisture isn't an issue.
Do a lot of research because I found prices range from $300 to $800 or more.
