I have a website called possess the dress which focuses on dresses (funnily enough lol) and it groups all the different styles and brands of dresses available at auction.
Just make sure you ask if they ship worldwide before bidding. I've had some fantastic bargains and most of the dresses i've bought have only been worn once. It still amazes me how much of a discount I can get compared to in store.
Here's the link:
http://possessthedress.co.uk/Store/coast-dress
Hope you find what you're looking for xx