One thing I purchased over the weekend was 2 4' x 6' solid rubber horse stall mats at my local Home Depot. One of those local rural specialty items on an end cap vs. listed online or in their mobile app. I cut them at the 3' halfway point with a box knife with new blade, creating 4 4' x 3' parking pads to go between the tires and the concrete. What I liked about these were the grooves that allowed any moisture to dissipate underneath each pad.
Warning: They are EXTREMELY HEAVY and unwieldy. A two person lift for sure.
Best,
-Mark