Below is a semi quick but permanent fix for a broken or cracked headlight assembly adjuster.  The problem is that the adjuster screws are mounted in a plastic fitting that is going to deteriorate and crack over time causing the headlight to go out of the adjustment or not be able to be adjusted at all.

This little plastic part is not something you can just order (that I'm aware of).  You could possible find a vendor who sells the whole assembly and pay big bucks for something you don't really need.  I chose to just fabricate a new plastic piece.

What I used was some scrape plastic which I think is a type of PVC plastic.  Basically it's flexible yet tough.  They use this type of plastic to machine parts from.  Where you can get it I'm not sure but almost any tough, flexible plastic should work.  The dimensions for the stock material needed to be about 1/2"x1/2" and about 1" long.

As you can see below, I cut a few "L" shaped pieces that roughly matched the dimensions of the original cracked adjusters.  The original adjusters were removed by drilling out the pop-rivets and removed. Then two holes were drilled in each piece.  One for the pop rivet hole and the other for the screw.  For the adjuster screw, I drilled a holes slightly smaller than the screw and just powered it into the hole creating the threads (it's only plastic).  Since the pop rivet hole was too deep for a pop rivet I just used a small bolt and nut to re-attach it to the headlamp assembly.

It's not rocket science but hey, it worked.  In fact it worked so well I may just replace all of them with this new design which would be more durable than the stock adjusters.  Each one took about 15 minutes to make using a coping saw to cut the plastic material and a drill to drill out the holes.  The rest was just putting it back together.

Below: from left to right.  Stock plastic, New adjusters (old below them), adjuster screws, drill bits to drill out holes (1/8" for small bolt, 3/16 (I think) to drill out for adjuster screw.