I agree with Belleofyourball, that these dresses dont look up to date or have much quality to them. You get what you pay for when ordering China made clothing. AND even though you provide measurements it still might not fit. Been there, done that.
What about the dresses listed for sale on this site?
Have you checked out LeNique Dancewear? They are in Los Angles, CA but do travel to different competitions.
Heres their FB page to look at some of dresses they have for sale.
https://www.facebook.com/leniquedesignerdancewear?fref=ts
Have you checked out Encore Ballroom Couture? They do rent some of these dresses. You can pay a fee and have them shipped to you for try on.
Http://www.encoreballroomcouture.com
Check with your local studio as well as your dance instructor for help. Many girls have dresses they no longer wear and would be happy to sell.
I set up a Dancers Trade day at my local studio. I was so impressed with how many girls set up tables to sell their gown and Latin dresses. Such choices in sizes, styles and prices!