Door Window Frame Gasket

I replaced all of my gaskets on the doors of my 71 Scamp with the exception of the vent window. There is one gasket that Im wondering if its available. Im looking for the seal or gasket for the leading edge of the main door windows where it touches the vent window frame.

Right now I only have what remains and seems to be a white type of plastic. If needed I can get a picture of the area Im talking about.