One of the best innovations in kids' clothing has to be the button-covered elastic sewn into waistbands to make them invisibly adjustable. D has a few pairs of pants without this feature, and while the length is just about perfect, they fall off his waist within minutes' of wear.
A good kid's belt is hard to find. Or rather, hard to pay for. Ralph Lauren and Janie & Jack both make adorable belts, but the prices are often higher than I spend on my own belts. Furthermore, they're usually designed to coordinate with very specific outfits, so they don't often mix well with the rest of a child's wardrobe.
It turns out that all you really need for a belt is two D rings, some ribbon, and some thread. Martha Stewart has a simple grossgrain ribbon pattern that you can make without a sewing machine. If you're up for coordinating outfits, you can use the same pattern to make bracelets. If you have access to a sewing machine, I recommend adding one additional step to Martha's pattern. After you have sewn along the folded edge of your ribbon, add a strip of quilting batting to make your belt a little thicker. This will help the belt fit more snugly into the belt loops. Making a wider belt will also help: instead of folding the ribbon, consider using two contrasting pieces of ribbon and 1.5" D rings.
And you're done!
You don't need to stop at ribbon; you can make a belt of out any material that will fit through a belt loop. Braided yarn, seasonal fabrics, and beads could all make fun belts. Fabric belts require a little more work, but you can find a great tutorial at Pretty Prudent that will help you make adorable seasonal belts.