The unit is sealed and you cannot replace the brushes in the motor, so it needs to be replaced completely. The correct type to use is a Domel 1200w 128mm unit.

To replace the motor, you need to disassemble the top part of the extractor. To do this:
Prise the top off the handle to expose the torx screws.
Remove these screws and then you can remove the black plastic casing to expose the wiring and the inner casing.
Disconnect the motor wiring from the switch – two spade connectors
Remove the torx screws that hold the power cable in place.
Remove the other torx screws around the casing (there is one deep one next to the top of the motor)
Remove the casing and feed the wires through. The motor should now be free to remove.
There are two rubber seals on the motor, one underneath and one on top of the large diameter fan housing. Retain these for the replacement.
There are little retaining latches on the spade connectors where they plug onto the motor, push these down with a small screwdriver blade while you pull the plugs off.

Reassembly is the reverse of the above steps. The two wires to the motor are not polarised, the motor is AC and doesn’t care which one goes where.