I believe the clockwork merchant at 1182, -560 should sell "Spell: Cure Poison". It is currently not on this merchants list. This is the merchant that sells various cures, heals, and resurrections in the clerics guild.
Either the spell was mistakenly missed or left out on purpose?
Not sure how it was in classic on live but according to EQTC this spell should be on the merchant:
http://www.eqtraders.com/items/show_item.php?item=23951