Where can i find a dress like Aria's (lucy hale) in pretty little liars? (read description for link)?

Where can i find a dress like Aria's (lucy hale) in pretty little
liars?

http://www.youtube.com/watch?v=HEpYAo7zijg

nothing over $50 please :)
its a black dress with a zipper. i'm not quite sure on the term of the
dress (so if you do please correct me) but it basically has a zipper
in the middle, and it's like extra extra scoop neck where like the
dress starts under the chest.