I've turned most everyone in our club on to the commercial kitchen floor mat material. You can buy a 3' x 3' square at Lowe's for $20. I've had mine for 3+ years. Made of thick rubber, it doesn't rot, tear, or chew. Easy to cut with a utility knife. Has holes for drainage, and a little bit of give. Also put it on the 4-wheeler instead of the diamond wire so the dog's toenails don't get hung. Best dog bargain I've ever found, so don't tell Lowes that this stuff has other uses!!!!
Here's the Lowe's listing: William Goodacre & Sons 3' x 3' Anti-Fatigue Industrial Mat.