Amulet of the Grinning Sun

Amulet of the Grinning Sun is a superior-quality equipment item that can be found within the instanced mission map Gorilla Grodd's Lab.

Source
The Amulet of the Grinning Sun can be found inside treasure chests encountered within the Gorilla Grodd's Lab mission map.

Treasure chest

 * Gorilla Grodd's Lab