I would have to assume if you are emulating SNES on the XBox you are running off of Coin Ops or similar software. That being said you should be able to go on amazon amd find a SNES to usb adapter or just purchase a usb plug and play SNES controller.
While Slippys suggestion is great it is my understanding that the Kade has been on pre order since March of 2015 and only people who backed the Kickstarter in late 2014 have received orders.