Ideas for a nearly 100% reliable portable data storage

If 10 GB capacity is sufficient, then a 16 GB USB flash drive is the best solution in terms of robustness and reliability. A (synchronized) second stick, however, will double your chances to get your data home safely. :)

Don't go with physical storage. Backup your data with Dropbox or to a server that is managed. Online space is pretty cheap, and you have full redundancy if they do daily backups.

Despite your bad experience with the Corsair Voyager GT, have you considered the Survivor series?

"I don't think you will find something realistic that is more reliable than a USB drive, so in order to increase your reliability you have to implement some form of redundancy.

You mention having to sync 8 gigs of data each day - is all of that data really changing every day? Could you perhaps have separate encrypted volumes for stuff that rarely changes (no need to sync every day, perhaps every week or month) and stuff that changes daily?"

"If you're not happy with either hard drives or USBs (which you're not), maybe you can go with an alternative approach: tape backup ... they're not as common as they used to be, but they're still here, used, and some people I know swear on them.

Apart from that (if it's only 16GB) you can also always burn 3 DVD-RWs."