Can you tell me how drug dealers get dianobol and all these other anabolic steroids?

Many places: For the most part, pharmaceutical drugs are diverted by corrupt workers in retail pharmacies, more so in wholesale pharmacies and the pharmaceutical companies themselves, as well as their warehouses. In some cases, there are chemists with their own labs who actually make the stuff, and that can be a problem because quality control isn't what it could be. Bad docs and clinics prescribe them too.