Never really liked the original plastic mounts, especially after mine have distorted due to heat from the normal halogen fittings. So have decided to try and create all metal replacements.
Here's a quick CAD render of initial design:


Left ring attaches to middle ring using bolts, 4 long one short. These 3 long bolts will also act as the mounts/adjusters and be oriented in an L - corner one being the anchor and top/bottom-right being for adjusting up/down and left/right respectively.
Right ring attaches to middle ring using four springs (via the little holes) and the headlight unit is captured between them.


Card mockup on a crystal halogen unit showing basic layout with paper fasteners instead of bolts. Obviously the 'retaining ring' is just laid on the bench here.