Hi, Joe; If you are referring to the clutch assembly, yes it can be replaced individually, but requires special tools.
Any shop that does A/C work should be able to handle it.
The air con compressor on my 2005 Vauxhall Astra club 1.4 is making a rattling noise on start up and generally between 1.5k and 2.5k rpm. I have found that this is due to the metal touching the outer casing on the bearing. Is there anyway to fix this without changing the whole unit?