Again pictures of the gun will help. There are number of different shapes o and configurations

The best place to post your want and perhaps find you part is on the Yard Sale forum of British Militaria.

I have been told the Vere Breslin in Pietermaritzberg, South Africa has a large inventory of parts and may even have your part. I do not have any contact info for him, someone here may.

In the past Mr. Breslin has been very reluctant to sell parts only. Recently he has expressed a desire to retire and my be more forthcoming now. I do know he has discussed selling his parts inventory.