So, I've got the mid-2011 MacBook Air. Thunderbolt but no USB3 built in. I've also got some USB3 hard drives that I use. I haven't been able to so far find an adapter so that I can get the speed of USB3 through my Thunderbolt port. Does such a thing exist? I know about the Belkin dock, but for $400 I could just buy a Thunderbolt hard drive.