Not sure if this is what you were after - when DD was toilet training DH rigged up an elaborate affair to protect his beloved car interior. So he bought plastic tablecloth material (can be cut to size required) from Clark Rubber/Spotlight etc and put this over the seat - holes cut for belt etc, then placed a towel for added absorbancy between the plastic and the car seat (was safe as seat was as secure as without the plastic). He wasn't fussed about the actual baby seat as the cover comes off quite easily and dries overnight. HTH