????????? https://www.brattons.com/PRO-PACK-SPARTON-HORN-REBUILD-KIT/productinfo/19777/

I think these Sparton horn parts are for much older horns than what you might be looking for but maybe this shop knows where to find what you are looking for and need?

Also this https://www.snydersantiqueauto.com/subgrouping.htm?cat=41718