You can use a raspberry pi 3 to connect to WiFi. Ethernet from Xbox to Rpi. A bonus to this is you can install xlink kai server on the pi also for online gaming.
Or there is this;
Vonets Wireless Mini Bridge dongle, WiFi Bridge Cable Convert RJ45 Ethernet Port to Wireless/WiFi Dongle, 300mbps WiFi Hotspot Signal Booster Extender Amplifier VAP11G-300 https://www.amazon.co.uk/dp/B014SK2H6W/ref=cm_sw_r_cp_apa_i_nAstEb7JZ4PE6
It requires a pc to set up initially but then just works