While it isn't the fastest storage media on the market, if you're looking for a secure portable drive with ample amounts of space Kingston's IronKey Vault Privacy has you covered with sizes starting at 480GB. It's hardware encryption keeps your files safe from the prying eyes of unwanted users.
The Kingston Ironkey Keypad 200 is an interesting device that provides a level of security for secure files that 007 would approve of. It also survived every torture test I put it through. However, I might recommend that if you use such a drive for secure file storage - buy two or more instead of a single unit. If you're going to have secure files, you wouldn't want to lose them by mistakenly misplacing a drive or some other mishap.