Someone else on the list called it "hardware screen". I had roll leftover from sealing out my buried downspouts, keeps the dogs from drinking stagment water. The screen squares are about 1/8" and the material is pretty stiff, almost bendable. Pretty sure it came from Lowes.
Galvanized Hardware Cloth
Did a quick Google, this is exactly what I used. Probably any fiberglass insulation would work, just make sure you get unfaced.
