Broken 50mm 'A' Series

Does anyone have a scrap 'A' Series lens that is available for spare parts?

In particular I am looking for the item below




The one on the left came out of my 50mm 1.4 and has you can just about make out the ring section has broken. The unbroken item is from a 28mm 2.8, the spring and ball head complete the assembly.

The complete assembly is actuated by the aperture ring and the ball head is is pushed into contact with the camera body when the lens is locked in the 'A' position.

thanks - Steve