Dog nail imprints on driver side rear door

My dog travels with me a great deal and has a habit of proping himself up on the top of the side door panel on the driver's side rear to stick his head out the window. He's a big dog and his nails have made several imprints in the plastic. I'd swear I saw a post somewhere about covers designed to protect that area. The post was from another dog owner with the same problem. He mentioned that the dog had trouble slipping down from the protector. Does any recall who it was or where the post is located. I've tried searching with different key words but no luck.