SRD:Amulet of Mighty Fists

Amulet of Mighty Fists: This amulet grants an enhancement bonus of +1 to +5 on attack and damage rolls with unarmed attacks and natural weapons.

Faint evocation; CL 5th; Craft Wondrous Item, greater magic fang, creator’s caster level must be at least three times the amulet’s bonus; Price 6,000 gp (+1), 24,000 gp (+2), 54,000 gp (+3), 96,000 gp (+4), 150,000 gp (+5).