There is a product that I am loving right now--heart shaped sunglasses. They are very lolita and very fun. Coincidentally they are inspired by the novel I am reading now, Lolita by Vladimir Nabokov. Because the sunglasses are a "fun" item, I don't recommend spending a lot of money on a pair. Fredflare.com and girlprops.com have them for under $20.
P.S. For once, an accessory will look a lot better on you than it does on this model.