Heres a simple and dirt cheap way to make link and pin couplers for cars like HLWs mini series The Basic components:
the HLW car, some sheet styrene, brass rod, and a 1/4 x 3/8 ABS tube
measure out 1inch segments and cut, trace the face plate on the styrene, it should be about 1/16 to 3/32 wider than the tube
Glue them together
clip the corners and file to a nice smooth rounded shape, L shaped, R clipped
Now using a 1/8 drillbit drill two holes in the end plate and use an Xacto to shape to a nice oval that opens to the full interior width.
Drill two holes, one 1/16 for the link and one larger for the mounting screw
drill a hole into the HLW car and mount with screw
top view mounted
now useing a needlenose, bend the brass wire,1/16 here, to an eybolt shape, I add a small donut of small diameter tube styrene to the base of the eyebolt
final pin as attached, shown with homemade link using same brass rod
And as coupled to another car. Total time, about 20 minutes tops All thats now needed is paint.
