The T2100 should use an EME278 drive, it's fairly unique in its dimensions and the location of the flex connector. It's not easy to replace the belt on these and sadly most of these laptop drives now do need a new belt, even the newer ones like the Citizen W1D (too small for your laptop) or the Matsushita EME279.
The Satellite 4xxx and 2xxx series use much later floppy drives which are direct drive so they don't have belts to fail, but the dimensions will not work for the Satellite T2100 sadly. Much too small and I don't even know that the pinouts are the same.
The Matsushita EME279 you can find in lots of the external caddies for the Satellite 4xx series, it's a much better drive to work on and I've found that replacement belts are easier to fit. I've installed an EME279 drive in my Toshiba T2130CS where I couldn't get its original EME278 working, so took the EME279 out from a spare external floppy caddy. The position of the cable connector is different but there's just enough slack on the original cable to use it with this new drive.
Here's what the correctly sized Toshiba floppy looks like, I don't know its part number but it's the taller one, not the flat external type you'd see in the later dark grey colour.
I've attached a 3d printable belt which I've printed in TPU in vase mode, it's the latest one that I use to repair EME279 drives. Also the latest one for the EME278, it's a taller belt and the EME278's design means that 3d printed belts don't work as well because there's no groove for the belt to sit in so it can rub against the PCB when moving.
