Dave, I think I have what you are looking for. It took me a while to find this when I was looking. This will divert the flow from one side to the other. I 3D printed some adapters for mine to reduce the diameter of the two outlets. I also have the same actuator you are using. I will probably 3D print something to mount the actuator to the vent.

https://airheatcoolcomfort.com/produ...-variable-flap

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