I’m sorry I can’t help with a source. To be honest I’m surprised a plastic part like that is fitted in the exhaust system. I can’t believe that Dufour would have fitted it. It looks like a piece of household waste pipe and not surprised if they are failing often.
What model Dufour is it? How old? Have you owned it from new? Whereabouts is this part fitted in the run of the exhaust?
Jeremy