Mage Spell Supply question (Poss. Spoiler)

[TwilightWaits]

So, after completing a certain quest involving a particular person in Everdale, I find myself lacking access to particular goods he sold, some of which would be rather useful.

Is there a way to replace this person, or another vendor who sells goods of a similar level/cost as his, or am I simply stuck praying they show up on the Port Kuudad vendor of the same type?

Yes, I realize that's a very vague way of describing said NPC, but I wanted to try and avoid mentioning things/names that would give who it is away (though anyone who completed the quest would know who I'm talking about).

[Randomizer]

There is a better vendor much, much later in the game.

You hit the dilemma spell casters face in this game. Do the right thing to finish the quest or wait because you need the merchant. This is one of those problems that you have to decide for yourself.