Art3d (2 Pack) 1/8" Thick Plexiglass Sheets - 36" x 24" PET Clear Sheets for Art Design，Craft Projects, Signs, DIY in Home, Wedding, Festival,Party,Office

I bought it on Amazon since they had the best price for the amount we needed. It’s 1/8” thick which is a nice middle ground so it is rigid but bends enough to easily get it in and out of the window frame. The only issue is a hard wind can rattle it in the frame. A wooden dowel as a spacer would probably solve the problem. We tried foam strips and the cats immediately tore them out and thanked us for the new toy. https://a.co/d/00UTnXhF