This one has worked great for me. It fits like a glove, protects the scope well, is light weight, doesn't add bulk, and just remove one snap then swing the lense cover to the side to use the scope. It's not cheap but neither is the scope.
The only downside I've noticed is you cant extend the sun shade without taking the cover completely off.
I bought the soft cover that Swarovski makes for the STS 80 at Sportsmans wearhouse. It works real good. They had one for the STS 65 to. Kind of expensive around $200.