Does anyone have an idea of what I can use under the litter box? This needs to be something that will fit into the corner snuggly and be able to be waterproof. My old cat is missing the box! The solids are easy enought to clean up, but not the liquid! I can't find a boot tray or anything the size I need....but wonder are there other things that will work? Do any of you facce the same dilemma? Help! Please!