I recently picked up this
16 Gb Sandisk Cruzer Fit USB micro stick at Amazon for $19.99.
It pretty much remains always inserted in the USB port at the back of my T4, even while my keyboard is taken in and out of its' case during transport.
It's the same color (black) as the rear of the keyboard and so tiny (1/4" protrusion) that it's hardly noticeable.
In fact if Yamaha ever comes out with a microArranger, because their arrangers come with a USB port vs Sd slot (Korg microArranger),
I think this would make an ideal Yamaha microArranger companion. - Scott