ive got a 2 storey hutch i dont about your cage, but i stapled bubble wrap round the 3 sides then stapled grow bags cut along the side and bottom and opened out i mainly did this as the roof was slightly leaky and didnt have funds at the time to re felt it, and so the roof and three sides have been stapled over the bubblewrap i didnt staple on the roof as i didnt want to cause more holes in the roof, but then its been so good ive left it, in wet weather i just put a piece of wood on the roof so it overlapps the front bit (where they can look out) depending on which way the winds blowing the rain doesnt seem to get in (note this doesnt work all the time) but my hutch is in a semi sheltered position, but if the weathers really bad i have spare bags and they cover the front (except the bit where they look out) so the hutch stays dry the whole time, doesnt look great but then bunnies dont really care what there cage looks like as long as they are warm and dry, if i can improvise i will, i would rather save the money aside for surprise vets fees and food and hay