Slightly off topic, how do companies find pharmaceutical companies in Mexico that have what they need? I would like to be a "proper prepper", which is easy to

Slightly off topic, how do companies find pharmaceutical companies in Mexico that have what they need? I would like to be a "proper prepper", which is easy to do for all things except BP medication. Pharmacies won't be available if society is ever put on hold and pharmacies won't sell me a case or crate. Would I need to become a lab or start a pharmacy myself?