Noooo idea how weight corresponds to clothing size for pretty much any weight range, so these are just guesses at something that might work. Have you tried the pants at Lane Bryant? You sound like you have the inverse of my figure, but so far their pants are the best I've found for fitting large hips & thighs with a smaller waist (in their blue circle fit). But the yellow / square fit are designed for the opposite figure, so they might work okay for you? I can't get a direct link to their size chart, but it looks like most of the yellow jeans have a 2" difference between the waist size and the low end of the corresponding hip size.
And if the Lane Bryant sizes are too big (the smallest yellow is for 34in waist, 36-39 in hips), Fashion Bug supposedly has the same cuts of jeans (but in smaller sizes). I also noticed when I was at Target recently that they seem to have changed the cuts of their jeans, although I had a little bit of difficulty figuring out what was supposed to be what. But that's a reasonably cheap option to try for pants you're going to grow down out of in short order anyway.
