I have wider hips and narrow thighs and a narrow waist. Not from weight (I'm pretty skinny) just from how I'm built. My problem is I cannot find slacks or chinos that fit. They have "relaxed" or "athletic" fit, but those assume both your hips and your thighs are big. My problem is that by the time the pants fit in the waist, the thighs are ridiculously baggy and look terrible. And tailoring just really isn't an option, especially not for that area - you'd basically have to take most of the garment apart.
Well, at first I wanted to suggest wearing black pants since they make you look skinnier, but since that's not what you're asking, my only suggestion is to take 'em to a tailor (since I really don't understand the problem here), though you could, of course, look around, maybe you'll find something, somewhere.