The first fragment is located at the Old graveyard in Lyria. Once you have completed the A Mourner from Wetterton battle, head north within the graveyard and you will come across a broken tomb, belonging to an elven mage. Choosing to explore the tomb will reward you with this fragment.
The second fragment can be found in Melitele's Temple, located just east of the Monastic Cemetary. After entering the side of the building and coming into the courtyard, you will come across a shrine and interacting with the shrine gives you the option to receive the fragment, at the cost of 250.
The third fragment can be acquired just south of Carduus Fields, next to the Yavina river. After traveling through the village and starting the For Better or Worse quest, a man just south of the village, next to the river will tell you about a magical artefact being pulled from the water, which at the price of either 100 or a decrease in morale, the third fragment is yours.