DIY top loading cat litter boxes! I bought two 18-gallon plastic storage containers with lids (about $7.50 each). I decided I liked the idea of using the lid to trap the spare litter crumbs, so I bought 2 feet of grey stair-tread carpet($4) to adhere to the lid with some carpet adhesive double stick tape. My total material cost for TWO boxes was less than $25 — a fraction of any of my store bought options.