Amazon.com: MOUYAT 15 Pack 18 x 24 Inch Large White Corrugated Plastic Sheets, 5/32 Inch 4mm Thick Waterproof Corrugated Plastic Sale Sign Blank Board for Dividers, Poster Board, Yard Making Signs : Industrial & Scientific
18 x 24 Corrugated Plastic Blank Sheets (6 Pack) for Signs and Guinea Pig Cages: Amazon.com: Industrial & Scientific
18 x 24 Standard Corrugated Plastic Business Signs
18x24 4mm Corrugated Plastic Sheets 10 Pack Yellow Waterproof Lightweight, Blank Boards Double Sided for Lawn Signs, Garage Sales and Real State. Various Sizes, Colors by WholesaleArtsFrames-com - Walmart.com