I have to say Most of the People on this forum are UK based, but being in italy yourself you probably have access to many online stores that would not ever show up to anyone in the UK.
Italy is obviously a full of parts for these cars, New parts will likely be what's called Pattern parts, that is parts made to fiat's specs by after market companies, but fiat is not likely to be making parts for these cars anymore.
eBay is a good source of parts for older cars but you have to be careful if buying "new" parts on eBay, that they are not cheap Chinese copies which are not up to spec.
Maybe another Italy based member will post here with some ideas for you but there are not that many Italian members on here, so equally you might not get any further response.