feel pais, but is true.
In some cases, the truss road nut es part of all truss road. AL most cannot change only the nut. Ypu need replace all truss road. you have three opcion
a) Some luthier, pierces the base of the neck with a drill and remove the truss road, and install a new cap drilling with a piece of wood. It's expensive and if it is not well done, the visual result is not good. Only recommended for high-cost bass.
b) Find and buy a new neck. Maybe you can find in ebay.
c) If the neck is more expensive... buy a new bass... (and the bad instrument, sell for parts)
Belzeboo tiene un diablo para ti...