sounds like you're looking to replace a part that isn't available separately... the link between the derailleur hanger and the knuckle of the derailleur body... the part labelled "#1" mounts it to the bike's Der. hanger, right?
You'll need to Replace the Entire Derailleur.. that link moves the derailleur pivot point rearward which improves other geometry for the derailleur.
the ones i've seen are Swedged (similar to Riveted) in place and are not removable/replaceable.