either you have one that needs to have the winding re-done (as in motor ran too long, overheated, and shorted) or you're looking for a spare. those who still use the PM braking system are holding on to any spare items they have for their own future needs.
in any case, you'd be best served to contact Richard Clark for servicing and returning your original parts or for seeking spare components. web link below. multiple ways to contact him. Electric motor shops used to be found in every city. today, it's a throw-away world so most of those shops have since closed operations.
RCG link =>