Using cheap bathmats is a really good idea if the dog likes to chew or they get ruined often. No sense in spending a bunch of money on something that will need to be replaced every couple of months. I was doing a search and I found these crate pads and they looked pretty cool.
West Paw Design Zoo Rest Pet Bed You can throw the entire thing in the washer if it gets dirty which is definitely a plus! There are some really nice dog beds on there too if you run a search by large dog beds.