I've been using the KATA E702 for several years. I realize it's much more expensive than the Optech Rainsleeve, but it's meant as a permanent solution, not a temporary one.
http://www.bhphotovideo.com/c/produc...Pro_Light.html
The tragic thing about the KATA pictures online is that they absolutely do not represent what they look like in real life (poor production photography IMO). The arms are definitely not as long as it would seem in the above link.
The entire camera and all the controls are visible through the transparent portion (which is flexible and easy to clean).
It is not cheap, but it will probably last a lifetime.
Unlike Richard, I do intentionally go out in the rain (I live on the west coast where it's been known to rain a bit).
Glenn