I second the previous poster for used children's clothes sales. Check local churches, they always seem to have one right about now. There's one called best brands resale (you can google it) in Wheaton on this Friday and Saturday.
I also always get used shoes on ebay. You can get shoes for as low as .99 plus shipping.
If all else fails, I have a shoe problem and end up with way too many shoes in every size for all my kids. If you want to pm me and let me know what kind you are looking for, I may be able to find one for you in a bin.