Anyone know how to replace the plastic on the outside of the door on a 2001 audi a4?

The piece of plastic that runs on the bottom of the outside of the drivers side door is falling off and is quite broken. Anyone know where to buy a new one and how much it'll cost+ how do I attach it?Anyone know how to replace the plastic on the outside of the door on a 2001 audi a4?Find the dealer for your audi you might have to pay more but you get a better quality