There is a Legacy version
here.
Berserker's Cloak
Item 12+Invested Primal 
Source Player Core 2 pg. 310Usage worn cloak;
Bulk 1
This bearskin includes the head and bared teeth of the mighty creature from which it was taken. When worn, the cloak drapes over your head and around your shoulders, imbuing you with a bear's ferocity. If you have the
Rage action, while raging, you grow jaws that deal 1d10 piercing damage and claws that deal 1d6 slashing damage and have the
agile trait. This transformation is a morph effect, and both the jaws and claws are unarmed attacks in the brawling weapon group. You gain the benefits of a +1
weapon potency rune and a
striking rune with these attacks (gaining a +1 item bonus to attack rolls and increasing the number of weapon damage dice by one).
If you have an
animal instinct and the bestial rage instinct ability, instead of gaining these unarmed attacks, your unarmed attacks from the bestial rage instinct ability gain the benefits of a +2
weapon potency rune and a
greater striking rune (granting a +2 item bonus to attack rolls and increasing the number of weapon damage dice by two).
Berserker's CloakItem 12
Source Player Core 2 pg. 310Price 2,000 gp
Bulk 1
Berserker's Cloak (Greater)Item 19
Source Player Core 2 pg. 310Price 40,000 gp
Bulk 1
You gain the benefits of a
+2 weapon potency rune and a
greater striking rune, or a
+3 weapon potency rune and a
major striking rune if you have an animal instinct and the bestial rage instinct ability.