We live in Australia, so not sure if you can get them where you are. Shadow has the extra large "Bono Fido" Stay Dry Futon. It is water proof(and pee proof, I poured a whole cup of water on it nothing got threw) and it is rip resistant. In fact one of my other dogs (pom x) put two chew holes in Shadows bed and the company are in the process of replacing it, free of cost.
It was a little costly to start with, but its been worth it. All 4 of my dogs now have one each.