Huh? What are you storing? Why does it need to be portable.. Why does it have to be small? Your wanting to store couple TB, why would you be using device sized 256GB devices if you need couple TB?

If you gave some details of what exactly your doing - it would be easier for people to suggest a way to accomplish it..

If I wanted smallest form factor to store 2TB of data, I would just get a 2TB ssd.. I think buffalo puts out a pretty small one, for around 100 bucks.. I think its smaller than 1x0.5x3 inches, And believe its suppose to be some sort of mil standard impact certified or something.. One sec, let me look up a link.

here you go https://www.buffalotech.com/products/ssd-put-rugged-and-portable-solid-state-drive-stick

Or you can just get a case for any nvme ssd and use that..