Amazon.com: Premium G10/FR4 Garolite Build Surface for 3D Printing - High Durability, Self-Releasing, Compatible with Ender + CR10S - Available in 1.5/2mm Thickness, 310x310mm & 235x235mm (2mm x 310mm x 310mm) :
Amazon.com: cncarbonfiber G10 FR4 300 335 2.0 Epoxy Fiberglass Composite Sheet Panel 2.0MM 11.8 x 13 Inch for DIY Models Part and Knife Handle 335 X 300 X 2.0MM : Industrial & Scientific
Amazon.com: 2Pcs FR-4 Epoxy Glass Cloth Fiberglass Sheet Epoxy Resin Insulating Board Processed into Various Types of Insulating Parts 150 x 200 x 2mm : Industrial & Scientific