Hi Cher,
I think you just have to experiment and try different things and hope it catches on. Since the digging is a natural instinct, it seems that little Miss HAS to do this in order to feel that her day is complete. I put an oblong basket with a cloth covering down for Tucker. (Actually, my sister got it for Xmas and didn't want it. I put it on the floor and Tucker did a flop inside of it the minute he investigated it. Love those flops bunnies do!) Last night he was digging in there and my neice, nephew and I were laughing at him because he was obviously on a mission.
The way he goes, I'd say he's digging a hole to China--just to see those little trouble makers of yours. The basket provides him a corner.The other thing he loves to do is if I have his travel cage out with some fresh litter in there, he'll get in there and dig until all of the litter is pushed out of the travel cage. Always angling toward the corner, mind you. I'd try to create an area that mimics a corner for him and just try different things. Get a cardboard box, put newspaper in there, see if he'll dig at that, or put a towel in there. They usually like fussing with a towel.
Good Luck! If you find something that works, do tell me as I'm curious now.
-Carolyn
P.S. I can't take credit for the tarp. I think that was Trobles1, but not sure.