[Arran]

Most people that have needed a special transformer had Heyboer rewind it, though I am sure they are not the only outfit that does this. Edcor might be an option for getting a custom transformer made, they seem to special in it, and are not a Boutique priced as Hammond seems to be these days. However unless there is definitely something wrong with the original power transformer a dirty, rusty exterior doesn't really tell you that it's a dud.
Regards
Arran