My guess is that you won't be able to with a High Sierra. Higher end packs (they cost more) generally have that option, but I would doubt that High Sierra is able to. They probably have one belt for all of those packs. Of course, it won't hurt to call them. They might have another style that also has a removable belt, but it is smaller, and they might be able to mate. Another option is to look at the replacement belts for other pack brands. You might find something that works.