According to the official FAQ from Nintendo of Japan, using a USBA to USBC charging cable is perfectly fine as long as it has a 56K OHM resistor the official Switch charging cable meets theseGames & Apps ;USB TypeC port HDMI HD port Charging Port Charge While Playing Keep your devise topped up, use an AC adapter or any Power Bank with a USB A to Type C adapter cable to charge the Nintendo Switch via the type C charging port
Nintendo Switch Power Adapter My Nintendo Store
