The combined 7 and 4 pin trailer outlet (plug and play) on my 2022 (so yours is different) comes with a 12 volt pin on the 7 pin side. I suspect all standard outlets will come with a 12 volt pin that you could tie into.

 

I'm looking for the male 8-pin OEM connector so I could pull the 12v from factory wiring behind the panel in the rear just as the 7-pin trailer connector appears to do without running a separate wire and fuse to the battery.

 

Bill- your post is pretty confusing. What are you attempting to add? Include part numbers, links or other information. If you're talking about the harness connection from the OEM trailer wiring kit where it connects to the vehicle wiring harness, that connector would come with the OEM wiring kit, you could purchase the kit and harvest the connector from it. I'm not sure where you would find that vehicle harness connector 'separate', if that's what you're looking for.

You could also simply buy the OEM Hyundai 7-pin wiring kit as per the part number you included above, and then use a 7-pin to 4-pin adapter (Example here, many others available on Amazon for sub $10). This would be the most OEM approach, not require any significant wiring modifications, and provide flexibility to use 4-pin or 7-pin (with brake controller if needed) trailers.