Have you any photos of the part and what has broken? Be useful to see some.
Worth an email to Atwood in case they can help. Otherwise as you are in the UK try "Bates Wharf Marine" (call the head office in Chertsey) who can supply Maxum parts or ask "ASAP Supplies". Both companies are really helpful and I'm sure will be able to help you.
Don't forget photos of before/ after and if you can update with part numbers I'm sure it will help others at some point.
Good luck! Lee
Another Day.....Another Bay!!