I have 2 skinny minnies (boy & girl) and 1 boy with the opposite problem. Jumping beans/Sonoma (from Kohls) and Old Navy work well for us.
I wish there were still a few places that had regular elastic waist (non-adjustable) slims. My 6-year old skinny hates the feel of adjustable waists, and it's almost impossible to find jeans without them these days. I think they have their merits and have always been good for my other 2, but they don't work at all for him. I have finally found some elastic waist non-slims that sort of work--I buy a size down for the waist which should be too short, but they still hang low enough at the waist that they end up being long enough.
