Funny you asked... I just changed mine today!
Part Number: A 463 421 00 12
I think that the front rotors were about $115 each.
I ordered them at the local dealership and they had them in 2-3 days.
I would also recommend purchasing one or two extra screws. I don't know what thier officail name is, but they hold the caliper on the hub, they cost an additional $.75. I had to drill one of them because the head was stripped out.
When you change the brake pads, make sure that you purchase 4 total brake wear sensors (two for each side).