Greetings,  You might be able to find all sorts of rubber matting by
searching for "switchboard mat."  I have not looked recently but did
at one time and found a supplier who had over 40 different patterns,
materials, and thicknesses.  I believe it is called switchboard mat
because it is used in electrical enclosures or something like that.

If memory serves me, the company was called Western Mat and was in the
San Francisco Bay area.  It was a while ago so maybe this material is
no longer available but they had some very nice choices for restoration
work.  You may have to buy a lot more than you need.

Best regards,
Spencer Chase
Garberville, Calif.
http://www.spencerserolls.com/