If you're budget-restricted, your best bet is this Alfred Sung Fitted Dress. It's a wonderful piece, while not very expensive. Another strong contender for your wardrobe is this J.Crew Fitted Dress. While the price of this piece is not very high, it will surely attract a lot of attention. You might also want to consider this DKNY Sheath Dress. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're looking for an item in the middle of the price range, look no further than this Clu Fitted Dress. This item doesn't cost the earth, but absolutely deserves a spot in your wardrobe. You might also want to consider this Joie Fitted Dress. It's an attractive option both price and quality-wise.