J.F.
This has been an issue with all three of my children!!! Unfortunately, with my girls, 18 and 16, there really wasn't a good solution, just did the best I could. A lot of times I had to order threw pennys catalog... Fortunately with my son, we are able to go to Childrens place. Seems to me the sizes run a little bigger and they fit better. Size 8 is great fit and has adjustable waist on just about every pair of pants I have bought from there.
Good Luck!!
J.