You can't cross-gender or cross-race armors on the modelviewer, you need a custom skin to do that. There's plenty of custom skins out there but I'm not sure if someone's particularly mapped this one yet, schoolgirl outfits are a dime a dozen and let's not acknowledge the nude skins. Scouring JP websites are obviously the best bet, just be wary about seeing something you would've lived a much happier life not seeing. (most skins are for Mithra only, male skins seem to be rather rare actually)