This part is identified as a pivot and is not used for adjustment . It is one of two.
On the left is the second pivot. On the right is the Left/Right adjustment nut.
In this image the Up/Down adjustment screw is more visible.
For older cars auto body supply shops have the threaded plastic inserts like the green one. I do not know if this one has been reproduced. Show it to a body shop that has been in business for a while, they may help you.
You might get a very good price on a headlight with a damaged lens at a junk yard and swap the part.