After haggling with Corbin for a rain cover for several months ending with a representive stating A) Corbin couldn't make one unless the bike was there, B) Their covers didn't fit anyway, so on and so forth, I purchased the saddlemen Seat Rain cover and within days it was delivered. It fits very well and serves the purpose for which I intended.
Haven't used the seat cover yet but it appiers to be what I was looking for. Just had the seat and passenger back rest done in leather. Wish they made a cover for the back rest also.