Whimsic Alley, your local fantasy shop, has to get rid of wizard robes in the new year. I'm guessing the lawsuit over using the Harry Potter brand is going into affect and they're getting rid of any retail not licensed.
From now until their stock runs out you can get deals on the robes and other wizard apparel. They will not restock, so unless you want to get this stuff online best get on a broom and fly over.