Am I right that you're asking about hammered dulcimer cases? If so, I would recommend the padded cloth case if you have the budget for it. It's a little bit nicer quality and easier to use and to carry (with a zipper instead of latches and a shoulder strap and pocket that the chipboard case doesn't have). Chipboard is kind of like a really thick cardboard - it's not rigid like a wooden or molded plastic case. It works really well as a budget option, but it doesn't have the features that the cloth case does, and it doesn't actually provide any better protection.
I'm afraid I don't know where you would find a used one that doesn't have a dulcimer inside already!