AC Duct Vent Covers

I am adding a 2nd AC in the bedroom of my fifth wheel, I currently have 3 duct outlets in the room. Does anyone know where I can find some replacement vent covers that have the ability to open or close the vents as needed. I would like to close these to force more air into the kitchen/living area when the bedroom AC is on, but still have the option to open them if needed.