Nimbus 86 Auto Trans source needed

 Trying to find a replacement Transmission (auto) for my 86 Nimbus. seems very difficult to find one with any life left in it, that doesn't cost the earth. Does anyone know if the Cordia or Colt Transmissions form the same period would fit the car exactly? Apart from the transmission the car is still in great order, we did the engine last year, no rust, excellent interior, so still not quite ready to scrap and we have four children so its very useful from that point of view. Any suggestions? We live in melbourne.

Thanks!!