I am in need of a kind of tub to set in the bottom of a cage.

Sturdy plastic, about 36x24", three or four inches deep. Like a very large litter box. All of these dimensions are approximate, as I can build the cage to fit the container. And it can't be too expensive.

I can't even think of what something like this would be used for, so I don't know where to look.

Any thoughts or directional indications would be welcome.

Sue