Try 'Michaels' Arts and Crafts. Bought the lighter color. Stained them and then clear coated with a couple coats of polyurethane, Built braces to have them seated securely.
Back panel was 1/4 red oak that was glued to frame and coated with about 5 coats of polyurethane and sealed with aquarium grade silicone. Glued to that backboard were two large pieces of Exo Terra Cork Board. Screen is perforated steel with 1/4" holes off center (not cricket proof - lol), but...