Help please - what to use as a dig box?

As I don't know what to use, I have two rabbits, and recently I've changed the indoor space for them, to give them more room (its now just over 8ftX4ft) but some of the area involves carpet, and Drew has dug a hole in it before I knew anything, so now I've got a very fetching old bed sheet on the floor, to protect it before I get anything else, but I'm wanting to put a dig box in there too, I was looking for a indoor GP cage or something, but until I can find one or buy one what can I use, I have a old plastic storage box that I was going to put some chinchilla sand in for now, would this do, and also what else could I put in a dig box at different times to keep them more entertained?

Any help would be much appreitated.