There is only a single location where you can purchase Apples in Bulk and that location is at Farmer Eda in Queensdale. Before I get started with telling you the different locations keep in mind in order to purchase any goods from a Karma vendor you must first complete the quest they have for you. That is of course if they have a quest available if not you'll be able to buy whatever they're selling right away.
Farmer Eda is located in the far northwestern end of Queensdale in the level 1 - 3 area of the zone. She is just west of Orchard Waypoint, if you port there you'll be able to run to her within seconds.