Classic Accessories 17 in. W x 17 in. D x 3 in. Thick Square Outdoor Seat Foam Cushion Insert 61-007-010907-RT - The Home Depot
Cubilan 18 in. x 18 in. Outdoor Water Resistance Decorative Pillows with Inserts for Patio Furniture, Throw Pillow (Pack of 2) B0B2J4N6JD - The Home Depot
Amazon.com: OTOSTAR Outdoor Throw Pillow Inserts - Pack of 2 Water Resistant Cushion Inner Pads for Patio Garden Coffee House Decorative Waterproof Pillow Inserts 12x20 Inch -White : Patio, Lawn & Garden
Sheets of Foam for Outdoor Cushions - FoamOrder.com