I do as my trailer is parked when not in use on the outside spot of a cover carport with full exposure to the west, so direct sun beams down on it until it goes down.
You can buy them at pretty well any RV supply shop. I have even seen them at Walmart in the RV section. Most are made for much larger
tires than what we have but the have a strap on the back so they can be tighten up - so far I haven't had one blow away even in the heavy winter winds we get here.