Mike
I guess the original type would have been Purdey , they could prolly sell you one smile
I guess you could contact them to see what material/diameter/thread was used on your gun? ...I'd love to know what they would charge for that little item ?....$750+?...If you contact them, let us know the price, would you?
How about a nice red Raybar???
I'm sure some one makes, or could make a good looking replacement once you know what your after.
What kind model & age ?
good luck
Franc