I’m actually quite surprised how chunky those USB sticks are, it certainly will not fit side-by-side with other USB devices with many computers.
A MicroSD card measures 15x11x1mm, so 8 x 256GB MicroSD cards would fit in the space of 30x11x4mm and give a total capacity of 2TB. Add casing and circuitry and I’m sure that would still fit in the size of a typical USB stick.
With that USB ‘brick’ dimensions, two MicroSD cards would easily lay flat side-by-side (15x22mm) within the depth (21mm) and width (27mm). So let’s say with electronics, the available length is 50mm, that would provide enough space for 100 x 256GB MicroSD cards, i.e. 25TB capacity.