Rubber-Cal Rubber-cal Recycled Rubber Sheet- 60a DurometeR-Smooth Finish- No Backing- 0.25" Thick x 24" Width x 48" Length- Black in the Rubber Sheets & Rolls department at Lowes.com
Silicone Closed Cell Sponge Rubber Sheet, 12" W x 12" L x 1/2" Thick, Orange-Red - Walmart.com
2pcs/lot 2mm Adhesive Silione Foam Rubber Sheet 163x203x2mm, Closed Cell Silicon Sponge Sheet High Temps Resist Red Mat - Gaskets - AliExpress