Will also drop from Precision Hookset, not just mooch.
Edit: You actually have the highest chance of getting on by using Precision Hookset with Brute Leech as bait. I want to say that 4/5 mooches from Aether Eye have resulted in "Crystalfin" instead.
I would even go as far as to say that if you get an HQ Aether Eye, you're better of just re-casting rather than mooching from it.