There are a few Armor Bonus materials I have yet to see on any playthrough. I've just been assuming they aren't in the public version. But recently, I've been seeing more item drops that I had never seen before. So I'm becoming less sure about that, and perhaps some of those items are just very rare?

The ones listed as materials but that I have definitely never seen are Aquavit, Enchanted Metal, Cold Gel, and Hard Leather. I have seen Spirit Dust, but only extremely rarely, and I *think* I've seen Enchanted Dust once, but I'm not quite sure. So it's possible that those other 4 are equally or even more rare, rather than nonexistent.