I’ve noticed that one of my bunnies (2~2.5 months old, approximately) have started digging and tearing (with his teeth but not ingesting) the flooring of his cage. I bought some wood (sold for bunnies) and I put a toilet paper roll there and he likes to bite them and flip them but he doesn’t scratch them. Whenever I catch him scratching, I put the wood at the spot where he scratches. He scratches it a bit and just stops and goes elsewhere – so i guess he doesn’t like scratching it.
I googled and people say concrete slabs or bricks are good but I live in Korea and we don’t have anything like Home Depot or anything. I even considered nabbing a brick from a construction site but they’re always fenced off 
I can buy a slab of marble but it seems to be not suitable for chewing and scratching but for cooling rabbits, is that correct?
Is there any other alternative? There is a lack of rabbit or anything other than dog/cat supplies here.
I live in an apartment building with a lot of dogs. I’m scared to take them outside to scratch concrete or dig in the dirt because other people are always walking their dogs. And one of my bunnies is very much not an outdoor bunny anyways.
*I would not like a digging box or something that messy as I live in a studio apartment and simply don’t have the space for the mess
And I’d like something safe for them to scratch without supervision when i’m at work and I feel like the mess that digging boxes will make won’t be good for them.