you guys need to think outside the box, a little. the material you are looking for is conveyer belting as used in grain and coal conveyer belts. its an industrial product still in common use, the "ribbing" on the back side is for grip or traction to keep the from slipping during inclement weather. whether you living farming or coal territory you should be able to find used belting either from implement sale or grain and coal processors. or you could buy new from either Goodyear or firestone.
I like the way you think, I searched all over for “fiber reinforced rubber”, so looking for elevator rubber will give me another avenue to check, though a quick search appears to have the same issue I ran into before, large quantity. Another quick observation is the back pattern may be difficult to near impossible to find. That all said I’ll spend time tonight looking.
I’m planning a salvage yard run this weekend and will hope to find something useful on that trip as the price will be greatly reduced
