I'm finding that light cured dental composites stick well to more than just bone. Although I can't recall if I've done this to a vintage, G*bson nylon nut I just did a black plastic PRS SE nut a couple of days ago and it worked great.
Be sure to file to clean material and I use a .010" file to file in a bit of a dovetail and a grove in the bottom of the larger nut slot grove. Something for the bonding agent to mechanically bite into is what I'm after.
Two beeps with the dental light for the bonding agent and then four beeps for the composite fill in a matching color for the nut. I'm always reminded of J Giles and his lyric about Goober Gober with the green teeth wen selecting a matching shade of color...
Then Four beeps with the selected fill.The stuff can gum up your files so I keep my older Stew-Mac nut slot files for filing dental composites and let them get gummed up.
Anyway I suspect it will work, I don't use the acid etch step one on plastic and instead exploit mechanical adhesion and I'm sure to rough up all surfaces for the same reason.
Plan B can be a nice mahogany shim being sure to not have end grain at the visible nut ends and then recut the slots to proper height.
Plan C can be a new bone nut with unbleached bone so Goober Gober with the green teeth gets a nut that looks as old as the guitar is.
Hope this helps Dave.