Letters are hung on the infamous oak trees of the Vallaki Outskirts and Mist Camp, and also just before the west entrance of Port-a-Lucine.
Send word to the Lady's Rest lodge to a "R.K.". Include which item you're willing to sell, its price, your name, and where you frequent or wish a letter returned.
I am currently seeking out:
Belt of Inertial Barrier
Cloak of Resistance
Mantle of the Black Roses
Vestments of Faith
Lotus Greaves
Aeolian Tempest
Be mindful with the purchase of one or more of these items I will stop seeking the others.