I'm trying to replace a headlight assembly on a 2014 Accent and can't seem to find an OEM assembly with a single 9-pin connector, which is what my current car has on it. The replacements seem to all come with separate 6-pin and 3-pin connectors. Either I need to get a wiring harness adapter or find a 9-pin headlight assembly. Anyone seen this before?

 

Something you might consider, if you cannot find the plug you need.
Get yourself a reasonably good test light , at least 10 or 12 shrink butt connectors (Blue for 14 gauge wire and red for 16 gauge wire) .

Of the 9 pins 1 should be for parking lamps
1 should be for signal lamp
1 should be for low beam
1 should be for high beam
1 should be for ground
1 should be for fog lamps if used
Don't know what the other 3 might be for , but looking at the other side should provide an answer,
You could place a spliced in connection for each of those to make the lights functionable. After the connections are made , heat the splices to shrink the connections to make a weather tight seal and add strength to the splice The other 3 could be for features possibly not on your vehicle. Close inspection could reveal if they are used at all.
Once done you probably would never need to open any of the wires again. If you need any further assistance with this , let us know.