condensate plastic or nylon nut??

i have a vaillient eco max 824 e,and when i turned on the radiators i notices water dripping from the bottom..........on inspecting i found that a white plastic/nylon nut that connects the condensate to the heat exchanger had perished and cracked....its a nut that screws onto the heat exchanger and the other end slides into the condensate and is held by a spring clip.......where can i find one of these nuts and what are they called