Hello. Just download some free mod with outfit and check the sources.
.rpym file could be anywhere inside mod's folder.
Mod folder structure from the wiki:
mods └───mod-id │ │ manifest.json │ │ item.rpym │ └───merge_folder │ └───images │ └───characters │ └───ino │ └───costume │ └───my_new_costume.webp
item.rpym file
init python: item_ino_my_new_costume = Outfit( name=__("New costume for Ino"), cost=100, descr=__("Item description"), char="Ino", lust=10, layer="costume", val="my_new_costume", shop="tenten", ptr=False, icon=KTCharInventoryPreview( char_name="ino", layers=ino_preview_layers + [("costume", "my_new_costume")], crop=ino_costume_inv_preview ), ) class MyNewCostumeModule(Module): subscribe_on_events = ["game_loaded"] def on_event(self, event): if not inv_shop.has_item(item_ino_my_new_costume): inv_shop.add(item)