I would suggest several of the companies which part-out Skymasters or those selling new surplus equipment, before calling a Cessna dealer. Several companies and their contacts (phone, email) can be found in my "backup" Skymaster website www.SkymasterUS.com
at the link "Purchasing Parts". Since you're in France, most of these can be contacted by email or via their website. Some of the companies listed don't have the website name, but it's generally obvious ( for instance, the website for Preferred Airparts is at www.preferredairparts.com
) or you can find it via Google. Your first contact should be with Don Nieser at Commodore.