Below are some of my favorites from The Dessy Group, one of the leading bridesmaid dress manufacturers who offers a huge variety of different styles and colors. Each dress can be ordered in at least one shade of white or ivory.
The complete collection can be found online, but almost every designer carries floor-length bridesmaid dresses in the style of a "real" wedding dress.
Have a look at the gorgeous dresses of Watters as well as Alexia Designs. Their websites have a tool that allows you to select by color which makes it easier and faster to find the perfect dress.