I can't imagine that anyone here will be able to help you find Imigran in Namibia, but maybe I'm wrong. If you do get them, be sure that you/your dad split them so he gets more use from them: Getting partial doses from sumatriptan injectors (Imitrex, Imigran, etc.) - ClusterBuster Files - ClusterBusters
The nasal spray, called Zomig, is similarly effective. There is also a sumatriptan nasal spray. This website says you can get that nasal spray "no questions asked." Is that true? Is the stuff reliable? Will they ship to you? I don't know the answers to any of those. Sumatriptan - Nasal Spray
Oxygen is very effective at stopping attacks. Can you get that? Could you set up a system using welding oxygen? Notes about welding O2 - ClusterBuster Files - ClusterBusters
DMT has been found to be a very effective abortive. Do you have any chance of getting (or making) that? DMT experiences and advice - Theory & Implementation - ClusterBusters