I ordered the Butler Creek caps from Cabelas recently for one of my scopes, and they were on back order for over 2 months before they finally shipped. Maybe that's not the case with the size you need, but I almost gave up on getting caps for my most recent scope.
If you've got a scope that Cabelas sells, and if you've got a Cabelas catalog handy, look up your scope and to the far right of the particular scope listing, you will see a order code number for the exact Butler Creek scope cover that you will need.