This is what I take to the Midlands nano to keep off the sun
. It has proved to be waterproof also
.
https://www.ebay.co.uk/itm/3x9m-Larg...SQY_muQDSHeWfw
Too big for you?
Maybe something like this:
https://www.ebay.co.uk/itm/Pop-up-Ga...I55NujyZHfokXw
I guess it depends upon how long you're anticipating keeping stuff in there and how severe, or not, this winter is.
Good luck with the search.
Andy.