Press NYCtourist recommends La Boutique Resale:

Boutique Stores NYC New York boutique stores are world-renowned for the quality of their merchandise. While generally more expensive than New York City department stores, boutique stores in NYC offer hand-crafted items by the hottest up-and-coming designers. If you like to shop (and who doesn't?), you simply cannot pass up the chance to check out all the fine boutique stores New York City has to offer.

List of Best Boutique Stores in NYC:

La Boutique Resale 1045 Madison Avenue, 2nd floor New York, NY 10075 212.517.8099