Cough
Back on topic.
For the black rubber stuff - try your local tyre dealer, and beg for an old truck inner tube (or two - you gotta blow one up and go down the beach!
) - and trim the good bits from the tube to fit. A couple of layers, folded from one piece of tube might do the job.
I can't really think what else would to the job - appart from grip mat - but that is full of holes!