also do you have many Vauxhall (holden) cdti cars over there, many of the cdti injectors are common to the jtd jtdm engines.
probably much cheaper.
you just need the code on the solenoid top face eg
use the number off yours , phone a diesel specialist they may have on the shelf or try a holden dealer may be much cheaper than alfa ?
give the numbers of yours and the numbers of the 2.4 ones you have
you cant swap 8v 10v injectors with 16v 20v injectors and vice versa
the 16v swapped with 20v will work but the amount they flow will be different so you will end up imbalanced , maybe no better off than before ?
you could swap all 4 ? but ideally would need the injector duration map changed to suit(part of a remap)
as above advice, id add a good injector cleaner beforehand to clean out any contaminants in the system, then if you do need to fit a replacement one a new fuel filter beforehand also gives best chance of not contaminating new injector.