Everyday is great with this Persona Q: Shadow of the Labyrinth downloadable content. If you want Nanako to cheer you on as a Persona navigator the Nanako Navi Voice DLC pack is for you. Atlus has the Nanako DLC pack on sale for 600 yen in Japan.
Marie from Persona 4: Golden is also available as a Navi Voice for 600 yen too.
These two characters are the final round of downloadable content for the Persona dungeon crawler. Atlus also has downloadable sub-personas like Thanatos from Persona 3 and the Velvet Room siblings available as Navi Voices too.