I need the locking wheel nut key for a 2001 Toyota Yaris?

I have a a 2001 Y Reg Toyota Yaris. I have the locking wheel nut kit, but seem to be missing the actual wheel nut key. (My guess is that a tyre place kept it by accident.)

Where can I buy a replacement wheel nut key from? (Obviously Toyota will probably sell them, but I want a cheap source.)