PDA 2.5 or 3.5 hard drive adapter, 500GB on your PPC

Does such a thing exist? It would allow you to connect a 2.5 or 3.5 hard drive to your Pocket PC via a CF or SD slot. I know there are CF to IDE converters which allow you to use a CF card as an IDE hard drive on your PC, but what I am looking for is the opposite. The converter would probably need its own power supply for the drive which is fine.