Amazon.com : Union Strong Foam Board 24X36 3/16" 10-Pack : Matte Finish High-Density Professional Use, Suitable for Presentations, Signboards, Arts and Crafts, Framing, Display (White, 24 x 36 x 3/16") : Office Products
Elmer's Foam Board 3/16" X 24" X 36" Black-on-black 81242 : Target