The best and most supportive waist belts will be on the "multiday backpacking versions'" typically 70 L and up. After all that is the size range where the waist belt is really needed. Many packs come in different sizes and/or can be adjusted so as to fit a wide range of torso sizes. It might be worth your while to visit a quality, specialized outdoors store and get fitted for a backpack. The belt should fall well below your navel, obviously.