Here's a close up of the transformer we use in all of our microphones. This is a custom wound, double shielded low loss transformer that has a response that is usable from 10Hz to about 1 MHz. If we sold these separately, we'd have to charge about $300 each, so don't even ask. Fortunately, we make enough of them to put in the mics. These transformers are unique and unlike any other ribbon microphone transformer.
A ribbon mic transformer must be properly matched to the specific ribbon motor, so even if you had this transformer, it would not necessarily be optimal for a given ribbon mic.