Black Polycarbonate Sheet - 1/4" Thick x 6" Wide x 6" Long
Coroplast Plastic cardboard 0.157-in T x 24-in W x 36-in L Black Corrugated Plastic Sheet in the Polycarbonate & Acrylic Sheets department at Lowes.com
Made in USA - Plastic Sheet: Polycarbonate, 1/2″ Thick, 48″ Long, Black - 63404834 - MSC Industrial Supply