The stables also drop wool (not everytime though). I remember that I bought an orange tree in the past because of those quests, but it's been in storage for a long time now, because the Glimmerbat Habitat drops oranges too and I'm usually always maxed on those. But then again, if I didn't had my orange tree when I had those quests, they would have taken a lot more time to complete. But today I need far more wool than oranges. I would buy the tree and later, if possible, the sheep.