WANTED: Mandel Adjusting Bolt for Columbia AB MacDonald

[john9ten]

Hello all

I am looking for the wingnut that is used to adjust the mandrel on an AB MacDonald when moving it from the Concert record playing position to the standard record playing position. Can anyone help? My AB came with a knurled nut, which while very good looking and inconspicuous, I'd like to switch for an original nut. Pic below shows what I have and what I need.

Thanks!

John