You can buy in NYC through their flagship SkinCeuticals SkinLab locations, authorized dermatologists, and high-end department stores. Flagship Locations (SkinLab)
Since SkinCeuticals is a medical-grade brand, many of the best places to buy are within clinical offices:
Found at 2211 Broadway, this location specializes in "great skin made easy" with professional skincare advice. Check out SkinCeuticals SkinLab UWS.