0.75-in x 4-ft x 8-ft Expanded Polystyrene Board Insulation in the Board Insulation department at Lowes.com
Super TUFF-R 2 in. x 4 ft. x 8 ft. R-13 Rigid Foam Board Insulation 99060464 - The Home Depot
Black Foam Sheets Self Adhesive Black Foam Padding Insulation Foam Sheets Neoprene Rubber Foam Sheet Anti Vibration Anti-Slip Foam Pad for Craft Furniture (8 Pcs, 4 x 4 x 3/4 Inch): Amazon.com: