About 10 years ago I bought a chunk of extra dense foam rubber from an upholstery place online. It is about 2 inches thick and is not the egg crate type foam, but solid and really heavy. The piece I bought was 3 feet x 6 feet. I cut it into two pieces, one 3'x2' for my small dog, and the other 3'x4' for my big dog. I sewed covers for them. They are still holding up great.

They are a b**ch to wash. I've run them through the jumbo front loader at a laundromat several times in their lifetimes. The big one won't fit in my washer. That is probably the only downside to these beds. In their old age, both dogs had/have the occasional accident, so I now have both beds encased in plastic tarps with fleecey blankets over the top. This way I only have to launder the fleece throws and can just sponge off the tarp under-covering.

My older collie can no longer get up onto his beloved couch, so he very much appreciates having his thick foam bed. My two were never the type to try to pick up their beds and move them around, but I doubt if they would be able to move these beds.

Sorry that I don't remember where I bought this super dense foam, but probably there are multiple upholstery places online that carry similar quality foam. I bought the highest grade, densest foam they sold. It wasn't cheap, but it's held up for a decade so it was worth the cost.

It occurred to me that if you get a thick and heavy foam bed for your doggie, you might want to leave one of his light-weight beds around for him to pick up and flail about, provided he isn't shredding or eating the bed. That way he wouldn't even bother trying to drag the heavy dog bed about. Since he enjoys this activity so much, I'd try to provide him with a bed specifically to drag and toss about, a toy basically, to avoid frustration with the new dense bed that won't budge.

Thanks for the visual of your dog attacking its bed...