Hard foam pad replacement I think this is an Arts and Craft question.

I am looking to replace a hard foam pad on a sander. Manufacture wants over $20, but I know I can make one for a lot less.

The pad would need to be 4 x 4 x 1/8 inch thick and fairly hard.

I can trim a sheet down.

Appreciate any ideas. :-)
I bought a piece of 1/16" rubber sheet. Glued it to bottom of old pad on sander.

https://www.dropbox.com/s/1ggm4j56fym0mdl/20180827_122005.jpg?dl=0

Because of the extra thickness, the sand paper is a little harder to fit between clamps.