The bronze gear is only to be used on billet roller cams. Everything else uses the steel gear. You can get one anywhere. Your dealer could get one for you too.
Correct, you only run that bronze gear when you run a roller cam. If you are running a high volume pump you will need a drive gear with a hardened shaft. Are you just replacing the distributor or is this a new build? If you are just replacing the distributor then there shouldn't be a need to mess with the gear drive.