Two come in the box, but I am using 3 or 4 bikes regularly.
The prices for a spare mount seems to be around a tenner, which my gut says is too much for a small piece of plastic you have to cable tie on (and re-usable cable ties aren't working as you have to do them up so tight).
So, anybody got spare mounts lying around I could have? Prices ranging from
Free
Loan
Loan and a BEER
A BEER
Bartering