For oem parts there are many places such as:
Just email them
pelican parts: http://www.pelicanparts.com/bmw/index.htm
As far as brakes go, for street use, people typically use Hawk HPS pads, and then you can use the Brembo or Zimmerman oe blank rotors.
This place sells HPS pads for about 90 a set with free shipping. They also have brembo blanks for about 50 a piece.