I have a Tire Rack Tire Garage outdoor tire storage bag, new in box. I used these at my old house when I stored tires outside. It's completely weatherproof -- you put the tires into a bag, and then there's another bag that pulls over the top. You then snap the two together and cinch down the straps. Very easy and protects them from the rain and sun.

New price from Tire Rack is $53 shipped. Please PM me any reasonable offers if interested.