City Quilter is totally the best quilt shop in NYC. Go to
http://www.cityquilter.com/
to see what they carry. If you want an overall guide to the Garment District and the myriad of amazing stores here, Paula Nadelstern has a great link on her site - NYC Garment District Guide.
http://www.paulanadelstern.com/fabric/guides/index.php
Enjoy yourself in NYC; it's a wonderful place.