While I like the idea of a magical horseshoe. ( I had a way different idea where this thread was going, a luck item or something similar)
If "3.0" information is usable the Necklace of Natural Attacks (Savage Species) is the best Natural weapon enhancement I have found, at least the best one that can apply to multiple natural weapons. So if that is the end result wanted, this might be a better option since animals can wear it.
Necklace of Natural Attacks (from Savage Species): The enhancement bonus on this necklace is applied to attack and damage rolls involving one or more of the wearer's natural weapons. In addition, any weapon special quality applied to this necklace also applies to those natural weapons. For instance, a +1 throwing returning necklace of natural weapons would apply its enhancement bonus as well as the throwing and returning special abilities to one or more of the wearer's natural weapons.
Caster Level: 3rd; Prerequisites: Craft Wondrous Item, Craft Magic Arms and Armor; Market Price: 600 gp, plus the cost of the enhancement bonuses, times by the number of natural weapons affected. (Thus, a +1 necklace of natural weapons that affects one natural weapon costs 2,600 gp. If the same necklace affects six natural weapons, it costs 15,600 gp.) Weight: --.
Edit: All druids should have this.