Easy, cheap modifications for your clarinet thumb rest to keep you comfortable and more injury free!
amazon.com/Vandoren-VMCX6-Mou...
www.ebay.com/itm/155030945053
www.ebay.com/itm/121717959622 (black)
I'm sure black silicone tubing would work as well. It might be easier to find it with the dimensions you need, and for cheaper, I just haven't ever tried it.