"Any good that I can do, or any kindness that I can show to any fellow creature, let me do it now. Let me not defer or neglect it, for I shall not pass this way again." - William Penn
Any auto parts store has tire covers. There's not a dimes worth of difference in them IMO. You will need to know the tire diameter to fit them properly.
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Before we had indoor storage I just leaned a couple of sheets of cut to fit exterior plywood against them. Wedged between the tires and the fender skirt.