Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)
I'll be selling my RED One MX package soon, which includes a Nikon mount. I'm not sure if you're still looking to repair the camera you already have, or if buying a working one would be more practical. It seems that most people who have the Nikon mount end up hanging on to them, or at least selling it off in a package when they get rid of the camera.
Alternatively, you could buy a brand new Nikon mount through RED directly (for full price). Looks like they still sell them.
Allstar and Optitek have some too. I went with Allstar because of the future possibilities to DSMC v1 and v2 mounting/support. I was in the same boat too, couldn't find a used one anywhere and especially ones that controlled Nikon-G digital lenses. :/