Winnebago has part numbers for everything. Since your rig is so new, it should be available from Winnebago although you may be able to find what you need elsewhere for a cheaper price. Hopefully you'll be able to just get the cover. If you have to buy the whole thing, I'd suggest switching the cover and keep the fan unit in case the original fails (as long as you can do so without removing the unit from the roof). There's no point in unnecessarily disturbing the sealing of the unit to the roof.