Anybody have some sources for some round rubber cushioning mounts ?

Need something that is about 1/4" -5/16" thick

approx. 1-1/2" in diameter with a 1/2" hole in the middle.

Thought about using some rubber casters taken out of their swivel mounts.

Also any sources for some full strips say the same thickness and 1-1/2" wide would work also.

Maybe baler belting sliced to the right width ?

Looking to cushion my Auger Mate in it's mounting cradle.

Normally it's bolted down tight into it's cradle but due to the customized mounting setup I came up with I will have four 1/2 bolt heads that will not let it sit flat in it's tray. Was looking to make up this bolt head thickness with rubber to provide cushioning.