Suggest you call your closest GW dealer - they can give you a price. Personally, I'd go to bid from several good local canvas makers. Not where you are but there are many near almost any coastal boating center.
If/when, we ever need to replace, I'd probably go that route. I'm betting you will get a better price plus the ability to customize. I would prefer to have the "smiley face" zippered openings on my front curtains, for instance.