Suburban rear window piece

[rod1701]

No idea what this is called but on the two rear side windows, the moulding doesn't go all the way around. There is about a 1" gap between the ends of the moulding. It looks like there should be a metal or plastic filler part . Although it rarely rather rains in So Cal, it gets into the truck on my newly dyed interior pieces when it does. Any help? Suggestions?
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