Western Digital offers the Western Digital My Passport Air 500GB USB 3.0 Portable External Hard Drive, model no. WDBBLW5000AAL-NEAP, for $44.99. With free shipping via coupon code "SEPFREESHIP", that's $11 under our June mention and the lowest total price we've seen. (It's a current low by $10.) It's USB-powered and features hardware encryption.