The Dia-Compes are nice, but they are exactly the same as vintage Dia-Compe 610s, which are widely available on eBay and inexpensive. weinmann and Mafac are both good choices.

The other option would be to take any set of dual pivots you have on hand and replace the bolt with a nutted one. Tektro and Spa Cycles in te UK sell these, but they may or may not fit your brakes. Trial and error I'm afraid.