I haven't had the issue myself so I haven't read up on it, but if its only the brushes, they are certainly replaceable and much cheaper than any replacement motor that you might find.
Have you got any experience with these kind of motors? They're very basic and usually there will be 4 brushes, each on a spring, and if there is still sufficient brush surface available you can just stretch the spring for more pressure.
The motor covers are usually just 2 or 4 screws that will expose the full motor.
If you want to give it a go, I can give you advice if you send photos of the motor partially stripped
If you want to replace the brushes, you can measure their width and height and find generic replacements online, then cut them shorter if they are too long.