1972 Duster , starting to tear into the build

Lowe's, Home Depot, and probably other hardware stores sell Maple plywood (and sometimes oak and other higher quality plywood varieties). Once you paint & carpet it, the actual grain pattern won't be visible. However, better-than-pine quality plywood will make for a more durable piece. Use your old panel to make a pattern to cut your new one. Add speaker cut-outs where you want them, and mount your clasps & hinges where they were on your old piece.