Ohhhhh - that part...
Pretty sure that one's welded in place.

New ? try
http://www.dbdepot.de/englisch/108/index_1024.html

Click on body panels 3. I think that's what you want.

Not sure of used sources - junkyard/dismantlers maybe ?
Look in Hemmings (pub) or HemmingsMotorNews.com
for sources.