Many years ago, S-L used French-made Leroy-Sumner motors in their windlasses. These motors had a short brush life, and the brushes could only be sourced from L-S and they had a very long lead time.
If this is the motor you have in your Sprint windlass, I would look for a different motor. The only supplier of replacement part that I know of is
http://slspares.co.uk/
Shipping from the UK is fast and at a reasonable cost. I used to highly recommend SL Spares, but after they refused to acknowledge a design flaw that caused me substantial grief on a cruise, I only mention them as a supplier.
Good luck.