Hello Top,
Are you talking about the cast arm from the cowl light body to the cowl trim band? Or the filler piece that connects the upper part of the cowl band to the lower part? My 29 had a chromed sheet metal filler piece that the light arm goes through to the cowl, and not pot metal. Perhaps early production used pot metal, while later in 29 they switched to the plated sheet metal. As for reproductions, I have not seen any thing listed for the 29 cowl lights. I was missing one light and looked for nearly 10 years. Finally found three at the same swap meet. If it is the arm that is broken, I think I have one of the lights stashed away somewhere, that had a good arm. Let me know any further details. :p