This is a very large scope of suppliers. A few that quickly come to my mind are Cameron, Kitz, KTM, Metso, Flowserve, Emerson/Virgo, etc., etc., etc. There can easily be over 1,000 companies making ball valves for "oil & gas", and that is not an exaggeration. There are roughly 600 manufacturer facilities certified to API-6D for upstream oil & gas ball valves alone.
Maybe a good place to start is to Google search "API composite list". Then look in the API-6D ball valve section and it will list all the approved certified vendors and their locations.