What enemy drops 4-slot weapons?

I need some for the AP Trick. Yeah. >_> <_< :p

You can buy them from some guy in Macalania, but there's a few conditions for him being there. You'll have to pay O'akas debt, and you'll have to talk to this guy when going through Mt. Gagazet your first time.

Or you can fight Adamantoise or Varuna inside Sin.

Wantz sells them in south Macalania (Thuder Plains exit), per Levian's conditions.

Half of the enemies at the Arena drop also 4Os weapons.

That's Wantz, right? How much of O'aka's debt do I have to pay? IIRC, I only paid 100 gil.