Check this item from bavauto.com
seems like a good idea if you don't want the int. to get too messy/damaged.
Part. # KP00020 GN
Protect your BMW's seats against dirt, water, dog hair and sharp nails. This heavy-duty pet pad features a rugged 420 denier polyester surface backed by waterproof PVC. The quilting is high-loft, insulating Dupont Hollofil for maximum pet comfort. And the backing is 210 denier rip-stop nylon. Easy to clean- simply hose off and hang to dry.