WD My Passport Essential SE 1TB USB 3.0 Portable Hard Drive (Black) for $79.00 shipped.  Here is a screenshot for your reference.  This portable USB drive does not require a separate power supply and is smaller than most of them, making it more convenient to carry around.  In addition, the USB 3.0 interface is backward-compatible with USB 2.0 and able to transfer data at 3x faster by using USB 3.0.  Most places have it for about $89.