Amazon.com : Corrugated Plastic Sheet for Indoor and Outdoor Use - 3/16 Inch Thick Poster Board, 24x36 Inches - Pack of 2 Black Plastic Board Sheets - Waterproof Coroplast Sheets and Lightweight
48" x 24" Corrugated Plastic Sheets - Short Flute White - USCutter
24x24 4mm Corrugated Plastic Sheets 10 Pack White Waterproof Lightweight, Blank Boards Double Sided for Lawn Signs, Garage Sales and Real State. Various Sizes, Colors by WholesaleArtsFrames-com - Walmart.com