SimpleTech by Hitachi Signature Mini 500GB Portable Hard Drive for $79.99 shipped. Here is a screenshot for your reference. Alternatively, it is available here for $84.99 shipped. This portable USB drive does not require a separate power supply like most external drives and is smaller than most of them, making it more convenient to carry around. Most places have this portable drive for about $100.
FS-U25/500E
SimpleTech Signature Mini 500GB Portable Hard Drive for $75.99 Shipped
SimpleTech Signature Mini 500GB Portable Hard Drive (Espresso) for $75.99 shipped. Here is a screenshot for your reference. This portable USB drive does not require a separate power supply like most external drives and is smaller than most of them, making it more convenient to carry around. Most places have it for about $100.