I got metal headlight adjusting screws from rare spares here's the link
http://www.rarespares.net.au/rarespares ... ct=HLK1000 scotts old rubber sell them aswell but I personally have had nothing but bad experiences dealing with them but try them if you want.
it looks like you get a spring and plastic retainer with it now( although the are for a Holden)
I only got the screws, you removed what's left of the datsun plastic adjusters from the 1600 headlight retaining rings and press the metal screws through the hole. And the screws gets held in by the grove in the head of the screw. It works perfectly and looks fine.
But I'm sure there are still plastic ones out there if you want
have a look here
http://northlandfasteners.biz/Store/index.php?cPath=26
or ring datsport they might know.