Both are on dead bodies that you must loot. The Tree Sentinels at the Hinterland also drop Blessings of Marika every time they die; there are two of them near the Site of Grace, so you can kill ...

Here's a guide on how to do it. From the Hinterland Site of Grace, follow the main path across several Tree Sentinels and a bridge until you reach the Hinterland Bridge Site of Grace. Keep going ...