I thought that's what was going on.
Yinn, it is highly unlikely that you will ever get a such a good amulet; you have to accept that first. Pursue it, yes; Expect it, no.
Second, being that it is a duped item, it is still your option to trade for one, but you are likely swapping legit self-found stuff for it, and if Blizzard ever decides to run "Rust Storm" again, it will probably disappear. It might even disappear if you enter a game where somebody else has one. So trading for one is a bad idea.
Third, don't ask for it in our trade forums, trading for known dupes is not allowed.
As far as coming up with something to use in its stead, you just have to know your build and your needs and look for something to fill those needs.