New bellows for old
It is not always necessary to replace damaged bellows. If it is just a matter of scuffed leather and a few pinholes at the corners, they can often be re-bound in leather and treated to a new set of decorative papers.
More serious damage however, like that above, demands new bellows - and perhaps you should take the opportunity to specify an extra fold. I can build new bellows on your existing wooden frames for any type and size of concertina, 6, 8
or 12 sided.