is in the hidden area of the Henne mines if you miss getting it the first time in Nabudis.
I had to make a correction as I never got it due to opening some of the forbidden chests.
Nabudis is so hard for someone who hasn't built up just running in and getting it very early in the game while possible is remote imo.
The chances of getting it are very remote in the mines due to the low precentages involved..
Someone did post a thread on his views of how to get it....increasing the chances of getting it in the mines.
Some people claim to have gotten several such spears.
I haven't bothered trying it.