Not sure if anyone here knows (or maybe the odds increase in 2.3) but I finally found a 5++ nekomata with two empty mod slots.
I save scummed just outside an NCPD in Wellsprings, bottom left. Granted I’m max level. I’m so lucky too, I gave up trying to find it through airdrops as I found an ugly BARGHEST one with one empty mod slot.
I just so happened to start doing NCPD scanners in Heywood and came across it, save scummed, and after 12 attempts, I got it.