Where can I find motor brushes ?

I've an old Hiatchi 12v cordless drill that has a 'sealed' motor and non replaceable brushes.
Wrong, the end cap easily comes away from the motor assembly offering up the brush housings which have internal measurements of 4mmx4mmx9mm.
Where can I find a pair of brushes that or very similar sixze, 'cos Hitachi won't sell me anything but a new £100 motor!