Based on experience this past weekend, swim noodles may be hard to find in the stores at this time of the year - the season apparently ends early. We tried several stores (WalMart, Dollar Stores, etc) in Tennessee and the clerks were amazed that there were none left. Anyway, a friend suggested using foam pipe insulation, available in different thicknesses at hardware stores and DIY stores. So I bought some 6' lengths. I like this stuff because it is already split, and tucks securely in place.
PS: In case you're wondering - with this 95º heat I was not worried about insulating against the cold. I was trying to keep field mice out of the trailer while we were gone for several weeks. Once the camper shells are down, there are a few places where rodents can gain entrance. Hope they don't like eating foam!!
Nick