How do you get a death certificate for someone when you are repeatedly told by everyone that there isn't one?

Depends on when the death occurred. If the death is relatively recent, then there will be a death certificate. You go to the gov and look up ordering a death certificate. Not just anyone can order the certificate, you have to have a legitimate reason (normally you need to be related). Most gov agencies are online. Look up your location and Vital Statistics, and it will be there.

If you are looking at a death that occurred abt 100 years ago, death certificates were not common and not issued as a rule. Just a simple entry in a book was all most gov'ts required.