Call these folks:Heyboer Transformer in Grand Haven MI( just google 'Heyboer' ). I have heard some of their SE outputs in a friend's amp.
What ever you decide upon, don't stand for some custom winder demanding payment up front with some huge and undefined wait period. Heyboer is net 30 for all its customers. Even custom, 2-of stuff...:)
There is *NO* reason to support such behaviour.
cheers,
Douglas