Help! I'm looking for a beautiful, simple, knee length dress to get married in on mid-tour leave. Any ideas?

I'm at a complete loss. I'm a soldier marrying the boy of my dreams when I go home on mid-tour leave in April. It's just going to be a simple, courthouse ceremony followed by lunch at my favorite "up-scale" pizzeria with a few family members and friends. I've been looking for a beautiful, simple, causal (and of course white) dress to wear but I'm hopeless at shopping. I don't even know where to start! I've looked at a few of my favorite stores online, but so far nothing has caught my eye. Does anyone have any suggestions on where I can look? A floral for spring could work, too. Even though I've opted not to have a traditional wedding because of my lifestyle in the military, I still want to blow my man out of the water on our big day! ;)