Hi guys. I know that finding Naul can be a real pain and to make things worse he has very low HP meaning that even if he is found he's often dead by the time you get to him. So I wanted to share what I know so far.
1) He seems to appear when / just after the Svara FATE.
2) I've know or hear people shout when he has been at these locations
X22, Y27
X15, Y28
X28, Y15
X30, Y12
X05, Y17
I hope this helps us all to find him. Good luck!!!