As far as i've gathered they are available in some of the new zones brought out by DoDh. You'll probably need a strong group as the mobs seem to hit like Planes mobs or worse. You can find a few of the items gathered from these zones in the baz for 25k on average. Most of the items seem to take quite a long time to level up and my not even be worth the end result to high level chars. These items ahve 6 levels for example. it gives you the % the current level is at. Some have more or less than 6 levels.