In order to obtain this item you must obtain 3 Mystery items and turn them into Mad Chief Researcher in Castle Jibral. The three parts are located as follows
Mystery Part Un - it’s in the dungeon behind the chief's village in Alumaru Village.
Mystery Part Deux - You obtain this from beating the Sea Cube Boss.
Mystery Part Trois - Get into your Mechat and head over to the Western Deserted Island in a chest.