I can tell you some brands NOT to try - Castelli or Luna or Louis Garneau. I'm snake hipped (read: no hips) and flat, and in these two brands I have to wear a size up from every other brand to get them to fit anywhere.

You might try Craft - I really like their jersies and they don't have elastic in the bottom. I bought it because it was very long waisted and I have a very long torso, but I think it would definitely be wide enough to fit over someone's hips.