You could have Theresa look in the Keystone specifically for them. Just have her do it ICly and I'll respond with her findings some time afterwards. The Keystone in Nyu-Taro covers common, easily accessible Classes, and will generally inform you of the conditions you need to clear in order to unlock them. More secretive classes (think hidden branches of ninja clans or whatever) requires either exploration, talking to people or just, y'know, buying information.