Red glasses of some kind.
I have to say, though, I love how sharp the costume looks already. Without the cutie marks or other identifiable features it's hard to pick it out as Rarity, but you're looking very stylish so you're on the right track definitely.
Oh, and I idea I just had is maybe on the back of the jacket or on the lapel or something you could applique Rarity's logo. The R with the eyes. Show that it's a Rarity design?