I would mention kratom as an unregulated substance sometimes used for focus but I usually get mercilessly downmodded even though it it topic-appropriate. I'm not advocating it for anyone, but it certainly exists and has its legitimate uses.

If anyone is looking for a drug solution, and I certainly wouldn't recommend using drugs to solve your problems, amphetamine would be the best thing, though it certainly has worse side effects than Modafanil. It worked for Erdos and is readily prescribed by psychiatrists to treat ADD, the disease of being unable to focus.