Nduja is a soft&spicy pork sausage from Calabria. I used Sobrasada which comes from the island of Mallorca which is more less the same. Maybe the version from Calabria is bit more spicy?! Anyway I think it is quite easy for you to find ´Nduja via Google or Amazon. I have to say this soft pork sausage has a lot of Umami.
https://www.wineberserkers.com/content/?p=5782
ENJOY
Martin