What kind of a cover are you after, how extensive do you want it to be, just the binnacle, the whole cockpit area?
If it has to be measured up first, then go to a reasonably local supplier unless either you can provide those measurements yourself and you don’t need their charges being inflated excessively with travel costs, or one where your supplier from some distance away has the measurements for the cover you want on file and can produce it from records they have kept from previous work. So perhaps the question you need answered is “Who is the main supplier of canvas work for Bavaria boats in your Washington/British Columbia area?”