You could look at this post maybe. Convert your game to a CIA, look at the CIA in a hexeditor in the position specified, and do up until you see "Open the DecTitleKey.bin file and get the decrypted key from it. (same format as EncTitleKey.bin file)". There's no guarantee that it'll work, but you could give it a shot. Otherwise, I don't know how to obtain a single title key.Symphony of Eternity, for one.