EVA foam is one of the best and easiest go-to materials for constructing costumes and props. It's light, inexpensive, versatile, and can easily be cut and heat-shaped for a snug fit. With enough time, patience, and the right tools, EVA foam can be finished to look like nearly any material. Use to create costume armor, headpieces, prop weapons, and other accessories.
These sheets are just under 2mm in thickness and come in 10 colors: red, orange, yellow, green, light blue, dark blue, pink, purple, white, and, of course, Adafruit black.
It's also easy to add NeoPixels and other electronic glowy goodness to your foam work. For more DIY prop inspiration, check out Erin St. Blaine's learn guide for Wonder Woman Bracers or the Ruiz Brothers' Obsidian Sword from Steven's Universe.