This simple tunic seems misshapen, but it actually fits perfectly well.

A formless vest allows you to briefly make your body amorphous, allowing you to avoid particularly deadly strikes. Once per day, you can activate this vest to take half of the damage dealt to you by a critical hit or sneak attack. You can activate the vest after damage has been determined, but before it has actually been dealt.

Prerequisites: Craft Wondrous Item, gaseous form.
Cost to Create: 1,500 gp (plus 200 gp for base item), 120 XP, 3 days.