Is this the piece you are wondering about? (fender side trim as mentioned above)
https://www.realoem.com/bmw/enUS/sho...diagId=51_2841 ?
Above is the pn for the chrome version. There is also an gloss black OEM version with different pn.
If so, be aware that the OEM trim piece/s has tabs that stick into holes in the fender, and you will have to either drill your fender (X5M fender comes with the holes), or cut the tabs off and stick the trim on with double adhesive tape only.