I also find that Seven jeans, Hudson's and True Religions are pretty forgiving.
I've gained 10 lbs in the last 6 months since I started triathlon training. And it's all in my thighs and butt. I can barely get my Seven jeans up over my thighs.
And I've given up any idea of wearing my junior size clothes again. They are all cut for thin legs.
I was complaining to my coach the other day about the weight gain and the size of my thighs. He said, "you're going to get huge!". Just what a girl wants to hear.