I just spent the last few weeks looking for a key and ended up buying one on YAJ. They can be hard to track down state-side so here are a couple alternatives:
It's reached the point where if someone bothers to note the polarities of the magnets in the original key, it might be viable to make repros. I won't be the one to do it, but a template key in which one could glue magnets should be easy for someone who models 3D prints.
It actually turned out that the control panel I thought was locked just needed a bit of elbow grease to get open! Rest of the locks on my NAC are missing so I plan on just replacing the whole set with something a bit more practical.