After 3 days hunting the same mobs looking for Nullity Sphere ID, I have finished with 100+ Instructions Discs ql 60-140. They all are rare and wanted discs. Where you can find them? Go SFH A-1000 city, move little North and you will see lots of: Mutants-Outlaw and Bileswarms. Those mobs carry lots of discs and there are lots of those mobs.
Hope this helps you to find your disc :-)