There's no oem option for the X6 as its wide as is its actually wider than a X5 with flared arches. You could go aftermarket but find a reputable seller as some have terrible fitment or you could go hamann flares which are high quality with perfect fitment but at 2300$ unpainted
Edit: not sure if they are still for sale
https://f15.bimmerpost.com/forums/sh....php?t=1703032