This item can be on either one of two bookcases. Both of these bookcases are located in the room with Pythoness Olrga. They are not visible from the doorway so you'll have to clear the room.
One bookcase is located on the right side of the room ( 105, -6, -120 ) /waypoint 105, -6, -120
One bookcase is located on the left side of the room ( 151, -7, -120 ) /waypoint 151, -7, -120
This Item can also be in the room that is located on the opposite side of the room Pythoness Olrga is in. Take the left from zone in till you come to your first room with bookshelves and weapons. It will be on the left side of the room, empy bookcase, just as in the picture.