I think in all cases you might have to adjust the pattern to get what you want.
Here's a nice list of patterns you might want to check if you haven't already: http://www.costumebeginner.com/malki...dent/robes.htm
Here is my personal favourite: http://www.mccallpattern.com/item/M4340.htm?tab=&page=1
because it wouldn't be so hard to modify (and the dress reminds me of Eowyn's shieldmaiden dress), but unfortunately, it's out of print now but you might be able to buy it from the net.
I hope that helps somehow.