window glass and vent window

At the top of the window channel and vent window there is a black rubber stop that is shaped to fit the front edge of the window glass. I am replacing the channel runner for the window and this piece is damaged on my car. Does anyone know of a source for this piece? It fits on top of the chrome channel between the vent window and window glass I haven't got a clue as to what it is called and I haven't found one. I need this. Can anyone help?