https://www.techradar.com/news/nintendos-new-wireless-nes-controllers-are-a-switch-online-exclusive

Announced during the latest Nintendo Direct on September 13, gamers will soon be able to purchase a pair of wireless NES controllers for the Nintendo Switch, allowing them to revisit the company's classic 8-bit titles as they were meant to be played. 

Much like the Switch's Joy-Con controllers, the wireless NES pads can be recharged by simply slotting them into the sides of your Switch console.