We had an ADCO cover for our last trailer. (Too windy here where it's parked, so we sold the cover.) You can order them custom made, but the non-custom ones can be strapped to mostly fit - just be sure to get one that's at least as long as your trailer!! Ours was a breathable cover on the sides (the top is impermeable, of course), and it came with zippers in about 4 different locations along the length of the trailer, so we could access at least one door. I'd recommend this brand; ours served us well for at least 3 winters.
