Great ideas, everyone!
Yeah, the size ranges are making it more difficult to buy retail. I will have a look in stores like Myer, etc. next time I am at the shops.
Thanks for the website StephMT, I've found a possible dress on that site when I looked today.
In case other people are looking as well, I found this site in my searches today: http://www.lightinthebox.com
Don't know if it's been mentioned on this site already, but they seem to have a lot of dresses for around $100 each. It looks like you can order custom sizes too. I'm not sure what the shipping is like though, I think you have to go through the shopping cart process to find out costs. Still, I've picked out a few to show my BMs...