Use the BMW part nbr for the tailgate emblem and do a google search that includes the words carbon fiber. That way...not only will you get the correct "size" Roundel emblem..but also you'll find the aftermarket carbon fiber emblems
Type
"BMW 51141970248 carbon fiber" into a google search box, then watch the huge list of venders/sellers of carbon fiber Roundels in the size you need appear.
BTW, I didn't verify the part nbr...I'm going off of what TX5 suggested in his reply above.