Handgrip of Proficiency (3.5e Equipment)
From D&D Wiki
Handgrip of Proficiency: The Handgrip of Proficiency is a flexible sheathe just right for a sword handle, but which can adjust shape to handle anything from a crossbow to even a small nub on the gripping surface of any non-ammunition weapon. Once the grip is applied, it can be used. At will, as a swift action you may cast Master's Touch (Spell Compendium) on its attached weapon, thus gaining proficiency in it for 1 full minute.
Removing or adding a handgrip is a move action which provokes attacks of opportunity.
Moderate divination;CL 1st; Craft Wondrous Item, Master's Touch (Spell Compendium); Cost 1,350gp, 108 XP, 2 Days; Market Price: 2,700 gp