Velvac mirrors get corrosion up in there and metal fatigue causes failures just like what you have photographed.
It looks like you are buying a new arm.
The head is easily swapped from the damaged arm to the new one....BUT, the head you have photographed is actually the wrong head for the right side position. That mirror in your photograph is a LEFT side mirror. Left side and right side mirrors are different based upon how they mount to the arm.
This photo shows a right side Velvac arm with the correct right side mirror. Note where the mirror mounts to the arm. The mirror mounts inboard and sticks out. Your mirror is mounted outboard and sticks in.
