I just realized that I had listed the upper flocked division channel twice. Here is the link for the lower flocked division channel.
https://www.rubbertherightway.com/19...85614-prd1.htm
Rubber The Right Way sells the UPPER flocked division channel as two 3' long pieces. One 3' long piece will do both vent window frames.
I have a 3' long piece and rivets available.