Just done the headlight mod on mine and one of my white arms was also snapped, exactly the same as yours Stu.
I just super glued it back together, it was broken and the headlight seemed fine in the car so never noticed before.
Obviously my OCD meant I had to fix it
Think it's main dealer part only but found the part numbers.
headlamp bracket (white)
drivers side 84927FE230
passenger side 84927FE220
