Hi there
To clarify, I think you're talking about the plastic piece that the leather of the gaiter attaches to, but which is invisible when fully assembled.
It isn't possible to buy only this part from Mini dealers' parts departments. They only do the entire gaiter at around £30 or so. I didn't bother.
However, if you hunt around (maybe put a "wanted" in) you can probably find a plastic gaiter for sale from someone who's fitted a leather one.
I've also broken mine, but it's not badly broken so I'm living with it.
Oli |