No info about availability.
Passive Transformer DI
This is a custom module that acts as a passive direct inject for mic level inputs. It uses a Marinair T.1442 transformer typically found in old Neve consoles and allows for another level of signal isolation between the modular system and the recording path.
The value is essentially the cost of parts. The most expensive component would be the Neve / Marinair transformer which is in the range of $250.