All the part #'s are listed for the 99-03 Grand ams in the
Tips and Maintenance subforum.
Pretty sure the window button bezel is in this particular thread.
99-03 Grand Am parts : Body & Structure/Doors & Glass/Interior Trim & Components
Look on the first post this picture.

I think this is that part,
11 retainer - 99-03 B GM#22603516
But You may not need a new clip.
A lot of the time it falls inside the door panel and sticks to the speaker magnet
We have the procedure for that in the
N-Body Appearance-Non-Performance
Hope that helps.