I bought this from Katherine's Creations also known as kgabor19 on Etsy.
http://www.etsy.com/shop/kgabor19/
HeritageClothesLine also made a version:
http://heritageclothesline.blogspot.com/2010/03/harriets-yellow-dress.html
A blog about American Girl, history, and miniature furniture, food, and fashion.