Connie, I have to warn you that mine isn't actually finished just yet, but......
I bought a 78 quart (I think that's the size) Sterilite clear container. I stole some beach sand from my boyfriend's beach front property which I plan on baking to kill the bacteria and bugs that may be in it. I'm going to connect the Sterilite container to the PD's cage by cutting a hole in the container and fitting a PVC tube that will run into the cage. I'm NOT cutting the wire on my cage, so I'm going to put a piece of wood over the bottom doorway and cut a hole in the middle of that to fit the PVC tube.
Clear as mud, right?
Instead of beach sand you can use regular kid's play sand that they sell in WalMart or Home Depot. I live in a rural area and have yet to find that stuff in the WalMart and Home Depot near me. I'm hoping they'll carry it now that the weather is warming up and people are building sand boxes for their kids.