You'll think I'm out of my head, but you have 2 "easy" choices, and one difficult one. Two easy choices: Replace the window or contact Creation Windows (I believe) parts & have them maybe bone one out of a warranty return window. Tougher choice - keep looking through catalogs. Those parts are not impossible, but extremely difficult to find aftermarket. The demand just isn't there enough to make it worthwhile for many of them, particularly the newer ones, to be manufactured aftermarket.
That being said, here is a link to a catalog page that has a few on it that you may or may not have seen.