Get some 1X2 lumber and 1/4" plywood. Make a tray style case with latches of your choice. Hinged style lock if needed. If the tray section is still too deep to play the keys line it with some firm foam or even a folded towel. Drill holes large enough in the back of the tray section for cables and paint the whole thing a color to match the room. Cost maybe $40 depending on the latches.
Important to make sure its on a stable stand or attached to a wall so it can't be pulled over