The Suncatcher

The Suncatcher +2 is carried by Isabella in Coast Way Forest, she'll give it to you if you side with her in her quest.

This small shield is one of the three items aside from Gentrus's Hand Mirror and Cloak of the Beluir Watch requested by Takos in Coast Way Crossing.

In-game description
"Shield of Barnassus: The Suncatcher Barnassus, a cleric of Lathander, created a polished bronze shield hundreds of years ago in order to battle a medusa rumored to be lurking in the catacombs beneath his city. Barnassus tracked the medusa to her lair and realized, almost too late, that what he faced was no ordinary medusa but one that had also succumbed to the curse of vampirism.

Barnassus closed his eyes and charged forward, ready to take down his enemy or die trying. Lathander rewarded Barnassus's bravery by filling the room with sunlight while the priest slew the medusa."