Elmer's 28" X 20" Foam Presentation Board - White : Target
White Foam Board - 30" x 40" x 3/16", Pkg of 10 - Walmart.com
Amazon.com : Union Premium Foam Board 18 x 24 x 3/16" 10-Pack : Matte Finish High-Density Professional Use, Perfect for Presentations, Signboards, Arts and Crafts, Framing, Display (White, 18x24) : Office Products