C5 Master Cylinder Tube Nuts

[Rhino]

One last piece of the puzzle for my brake install is tube nuts for the C5 master cylinder.

It appears that the front port is M12 x 1.0, and the rear is M12 x 1.5. The issue I'm having is that I can't find anyone who can supply the M12 x 1.5 tube nut for use on a 3/16 line.

I've seen people mention they were able to find M12 x 1.5 fittings for 3/16 tube, however I have yet to come across a thread which provides part numbers or where they were sourced from.
Does anyone have any guesses to where I could source them?

Baring any breakthroughs there:
I have the stock fittings. The rear port originally used a 6mm tube. The difference between 6mm (.236) and 3/16 (.187) is a hare under .005
While that seems like a relatively small difference, I don't want to do anything to jeopardize my safety on a critical system such as brakes. Could the original nut be reused for the 3/16 lines? Another option I'm considering is using 6mm line from the rear port into my proportioning valve.