I thought about Clark too, but I'm not sure where he'd fit in the list. Similarly, the second boss (no name to avoid spoilers) in "Son of Crawmerax" can drop the Thunderball Fists and Tinderbox.
I noticed that in the short Pearlescents section towards the end (in between Legendaries and Seraphs), you have "slot machines (in all three modes)". AFAIK, that only applies to the Flamerock slots. Can you even win pearls from the Moxxi or Torgue machines? I really don't know. I never played the Torgue machines much, and haven't played the Moxxi machines much in a long time.