Using a twelve volt fan is far more efficient the way the Niro is configured. Available in any auto parts store or online. But as Michael Jones points out, you do have to leave the car on if you want it to run all night. Some Niro and Ioniq owners leave the car on with AC all night while car camping. I haven't tried this myself, but I might this summer. At some point, it will probably cycle the engine, not sure how long the traction battery will last running AC.
2018 Kia LX HEV Metal Stream with Advanced Tech