Rock Auto/Power Stop for sure
https://www.rockauto.com/en/catalog/bmw,2011,550i,4.4l+v8+turbocharged,1446914,brake+&+wheel+hub,rotor+&+brake+pad+kit,13824
Zeckhausen racing is where I usually got mine for the Bm'ers.
https://www.zeckhausen.com/catalog/index.php?cPath=3_4_3520_3522
Centric rotors are fine. Used to use EBC pads from there, but now it seems he carries Hawk and Porterfield which I know nothing about. Personally I would look for a lower dust option...