The dealer does not sell this rubber piece separately, you have to buy the entire cowl to get it and pay stupid money (over $400 list). Does anyone work in the auto glass industry know if there is some kind of generic grooved weatherstripping that will work as the rubber seal between plastic cowl and windshield? It should just snap into place.
A salvage yard be your best bet for an exact match. If you were to try an alternative...a piece of door edge protector might work, if you could get it in the right length.