I have repaired Cinq and Sei headlamps before when the adjuster has broken by using springs to hook around the headlamp, and then around the headlamp surround, this pulls it back against the adjuster and the rubber cap still fits in place
This means you can still screw the adjuster in and out to get correct alignment, but spring holds it tight so no wobbly MOT failing headlamps.
The springs I used were just ones I had in garage, but they may have been Cinq steering wheel horn springs, obvious to those who have taken off Cinq steering wheels, or something similar is RC Nitro car suspension springs, they are about same size.
I've not pictures so can't really give any more info, but it is straight forward.