Model A Horns 1-231-577-1375 (Michigan) They are in the vendors list on this forum.
How about Bill Randall, The Horn Shop, Rome, NY 1-315-336-8841, he is not listed in the forums vendor list but he has been mentioned in the past.
I also have on my list, Model A Horns (Horn repair, rebuilding): Jim Diehl - 2534 Duffy Dr. Cadillac, MI 49601 1-231-577-1375