Elecom is going to release the USB 3.0 compliant a dime-sized ultra-small USB flash drive "MF-SU3 series" (8GB, 16GB, 32GB) in mid July.
Since it's extremely compact (W21.5xD12.2xH4.6mm), you might be concerned about accidentally dropping or misplacing it. If so, you can attach a strap to the strap hole on the USB flash drive.
Compatible OS: Windows 8/7, Vista, XP, Mac OS X (10.6～10.8)
Weight: About 3g