Pleas explain what you mean by cockpit cover. Do you mean a helm cover or drop curtains for front, sides, and back? Perhaps you are looking for a storage (no windows) storage cover.
I suppose that you can find a hem cover but if not, any canvas shop can make one. A few things to note. Usually a canvas shop will measure and fabricate a cover but without the snaps. The shop will install the snaps on you actual boat. That makes sure they line up. More importantly, if you have curtains, install them before the helm cover snaps are installed to make sure the snaps are in the right locations. Often the sliding type on the windshield frame will have moved. After the curtains are installed, remove them carefully so that the snaps stay in place and then have the snaps installed in the new helm cover. That way switching between the curtains and the helm cover won't require snaps to be readjusted. I know from experience
Here is an example of a helm cover
www.rnr-marine.com