Update:
This cloak was the reward for a GM event quest. Unless that event is again triggered by a GM, you may as well consider this a "no longer drops" item.
The quest giver was a druid NPC at the old non-working druid ring in Lesser Fay near the entrance to Mistmoore. If you see him there, you can hail him and see if the quest works...but as I said, this is a GM event thing so the odds of finding him up are not good.