I'm not totally sure on this one, but I don't think you can link an item to the animation system of a character (not in TLK imo).
I had already tried to attach the warlock's wings from MoP and they don't seems to follow the animations of the player, but like I said, i'm really not sure on this one, perhaps someone like Rangorn or Alastor already made it since they're at a much higher level than i'm on this kind of things from the topics i've read back then.
You can either look in the events from m2 interacting with the emotes/animations from the player like the gold challenge rewards shoulders or the warlock's wings from MoP, or hope for an answer with someone with more knowledge, sorry.
tl;dr : I know it can be done if you link the item in a geoset in the model itself, but as a custom item with the animation reacting on the player animations, well, i don't know, maybe ?