The thing to keep in mind about Neopets is that they've been online for about 15 years, so they've had a lot of time to come up with that amount of items.
You could also work on batches of items for features. If you're working on an explore feature then make some items that the player can find while clicking around the map. Or if you're adding a new area, work on some themed item for that place. New Npc, make some items themed after them.
Springhole also has good generators for more general items.