I can't tell by the photos on the thickness of the original rubber but you could cut your own out of rubber stall mat - horse stall mat. It's tough as nails and useful for other projects.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy