Acquired:
Bodahn in the PC's camp.
Sometimes it can be found in the chest in Marjolaine's home.
Awakening:
You have to complete the Trade Must Flow quest (end it by talking to Mistress Woolsey), and visit Yuriah after that, in order to buy the trancing. He should have a quest sign and cutscene at this point, if not, leave the keep and return.
Crafted
Tracing
Sold by Yuriah in Vigil's Keep after 1 Upgrade