I'm sorry if this one has been brought up before, but it seems rather silly for there to be amulets and armor that affect your resistance to a status that, to my knowledge, can only be self inflicted by throwing a sleep vial near yourself.

So my suggestion is a set of weapons that can inflict sleep (damage type is up to you guys, though I think one of them being shadow would be interesting, could call it the Nightmare Blade or something) and some enemies that can inflict it as well.

All in all, I just find it to be a waste of space and if you aren't going to do anything with it, pitch it!