Plexiglass sheets are available for purchase at ePlastics, Home Depot and Lowe's, as of 2015. Additional sources of plexiglass and acrylic sheets include Professional Plastics and eBay.
EPlastics is an authorized Plexiglas plastics distributor, and it features a complete collection of plexiglass and acrylic sheets in a number of categories including clear sheets, bronze and gray, translucent color and transparent color. The sheets are available in multiple sizes and thicknesses up to 4 inches.
Home Depot carries a wide variety of Optix-, Fabback- and Plaskolit-brand acrylic sheets. The sheets are available in clear, colored, frosted and mirrored surface types. Lowe's acrylic sheet brands include Blue Hawk, Design It, Duraplex and Gardner Glass Products.