Classic clickies with Lull-like effect?
 

I'm challenging myself to play a Tribunal-worshipping Barbarian Shaman and solo as long as possible. Lately I've noticed there are a ton of tightly packed camps that would be otherwise amazing XP. It would be effortless to break them up as a Druid with Harmony or as a Cleric with Lull but as a Shaman there's nothing I could do.

I did my research and found out that all the aggro range reduction clickies came out in Kunark, and the only one available in Classic is the Erudite Cleric Quellious necklace. Do I have to be a Quellious worshipping cleric to do the quest and click them from my inventory? If not are there any alternatives? (clickies with lull/harmo effects)

You are out of luck. You should consider just rolling your own druid since harmony is only a level 5 spell and cannot be resisted.