Amazon.com: Bumpers Replacement LB RB Button for Xbox Series X/S Controllers,2 Pack Shoulder Trigger Buttons for Xbox Series Controller(NOT for Elite Controller) : Video Games
Steam Deck natively recognizes the PS3 controller. Simply plug it in via USB, wait for Steam OS to recognize it, then unplug USB cable and it will work over Bluetooth without needing to pair it. : r/SteamDeck