I think it is glued on with glass trim adhesive, and guide rides in the track all the way to the top. Think you can order some from here.
https://www.buypgwautoglass.com/default.asp?REG=&UserType=&ShipToNo=&PB=0
https://www.buypgwautoglass.com/default.asp?REG=&UserType=&ShipToNo=&PB=0