The GBros. Wireless Adapter from 8BitDo will give Super Smash Bros. Ultimate players an alternative option for playing with GameCube controllers.
Releasing December 7, the $20 accessory connects to wired GameCube controllers via a bluetooth receiver to the cut the cord between the Switch console and your controller.
Though still not fully wireless, the GBros. adapter ensures that you don’t have to worry about how far you sit from your console. The adapter has 30 hours of battery life and can be charged with a USB-C cable or powered by two AA batteries.
Source: IGN.com 8BitDo Wireless Adapter Will Let You Use Your Old Wired GameCube Controllers on Switch