General polity books on Tilea and Estalia are likely to be found in the Aquila Academy. Those two are the last two polities in the Old World we don't have books on, so that'll round out our collection nicely, and we're also supposed to map those areas sometime (though there doesn't seem to be much appetite for actually taking that action). I'm actually not sure which is more likely to have books on elves between the Aquila Academy and the University - Tilea is a costal nation, and Estalia also has a pretty long coast, so maybe they deal with elves more?
Also, the Nuln Aqulia Academy is notable in canon for taking the stance that the whole "we should do another Arabyan crusade" thing is moronic and they should focus on Chaos instead. I don't know if the Aqulia Academies' weird Araby obsession is quest canon, but the Knights of the Blazing Sun joining Magnus in the Great War definitely is, so Aquila Academy is probably going to have books on enemies of men that might be relevant to Mathilde.
Finally, the Nuln Aqulia Academy is associated with the Knights of the Blazing Sun IIRC, and that order was part of the reconquest of K8P, and therefore something something 5d chess.