where can I buy a diaphram kit for a CHAFFOTEAUX ET MAURY gas hot water sys?

Where can I buy a diaphram kit for a CHAFFOTEAUX ET MAURY gas hot water system. The part number for the diaphragm is 25809/20 The pilot light is on but the flame doesnt come up when the tap is turned on. I have had the problem before and the plumber has fixed it by replacing the rubber diaphram. He now says he cant buy the part any more in Western Australia ?? Can anyone out there please guide me to a source for parts.