That's so dumb!!
Bmw dealerships are ridiculous. I wanted to change my kidney grill to gloss black. They told me the whole bumper needs to be removed and it's a 2 hour job! I did it in 5 mins lol
In your case, I would just buy a new OEM part and get it painted. Once you take the cerium gray ones off, sell them. People pay good amount of money for those.
This is a link where you can get the part from
https://www.getbmwparts.com/oem-part...QtNGwtdjgtZ2Fz
Incase you also want to change your sidewall piece this is a link for that part
https://www.getbmwparts.com/oem-part...QtNGwtdjgtZ2Fz