Wanted: Motor insert piece

[aladds]

Does anyone know where I can get the motor insert piece from? The bit which goes inside the gearbox and holds the metal pins for the little gears. Mine is ok, but the output shaft is a bit short, which means an 18mm belt sticks out by about 2 or 3 mm, which causes it to slip off all the time...

So obviously I only want a long one!

Or: Chas, are you selling metal inserts yet?

Thanks!