The ONLY place I am aware of to get Ductwork is from the OEM's. Jayco(and others) use the type in your pics. The few times I had to replace a duct(Newmar and Jayco), they sent the ducts by freight. Since you have the rafters exposed, the ducts just bend and slide in place and you cut to fit. You could buy thin foam board and make your own. Just use trial and error to figure out how to cut and bend to form the rectangle. Then use the foil tape. You could also make it out of 1/8(3/16) luan and have a good strong duct system. Doug
