Immortality
Prerequisite: You must be at least a 20th-level Wizard to select this discovery.
Benefit: You discover a cure for aging, and from this point forward you take no penalty to your physical ability scores from advanced age. If you are already taking such penalties, they are removed at this time. This is an extraordinary ability.
Did nobody tell him about this Arcane Discovery? I mean, he is 20th level or higher, right?
He probably took a few levels in a prestige class and now he can't get to 20th level as a wizard because his GM isn't using any epic rules.
Inner sea magic puts him at 19th level. Which fits as he is searching for that right now. He is ailing and 20th may be out of his reach.
Just a note: AT 19th level he is god-like in power to the common folk. Very few people on Golarion have the power he does. In the Inner sea magic list he is only out powered by Rune lords, Gods, former gods and Nex.
If he wasn't so paranoid he could have a druid kill and reincarnate him.
Alternatively he could theoretically go to a large enough city to contract services with an 18th level witch and have her Force Reincarnate him (to circumvent the worry of not being brought back after the initial kill).
An 18th level witch or 18th level anything would be damned rare in golarion. He is 19th level and can fake being a God. There are maybe a handful of 18th level witchs in the whole of the world and those are powers unto them selves or well hidden. And the chance of her having that power and be willing to use it on him is slim to none really.