Pretty Sure BMW will sell you the parts, any parts, if you have the $$$, they will not even ask you the VIN Number, go down to the local deal, tell them you need X parts, and have Y Cash in hand they say "here you go"

Tesla attempting to turn cars in iPhone Walled Garden where you need approval to fix them and only allow to use Manufacture Approved Repair Centers likely will be the down fall of this, as people will not stand for this long term like they have with Cell phones, ironically this type of Automotive lock down (which Tesla is far from the only offender) will likely be the cause of Right to Repair laws being passed in most states very soon that will extend to all manner of electronics including Cell Phones