Upholstery Foam 6"T x 30"W x 80"L (Semi Firm Plus) Density 1.8#, Compression 36ILD Sofa Seat Replacement Cushions, Foam Padding, Foam Cushion - Walmart.com
Deluxe Foam Replacement Filling
Amazon.com: Nigoone Upholstery Foam Cushion 5"X 24"X 24" Square Foam Replacement Foam for Couch Chair Seat Padding, High Density Thick-Custom Pillow and Craft Foam Upholstery Supplies, 5 Inch Thick : Everything Else
Amazon.com: HOMBYS Couch Cushion Replacement Wrapped with Polyester Batting, High Density Couch Cushions Inserts with Dacron Fiber Layer,Upholstery Cushion Padding with Removable Cover,6 inch Thick,24"x24",1 Pcs : Home & Kitchen