It appears from the picture in the manual, that you should be able to take the end plate off fairly easily and see where the wires are hooked up . It should be similar to the Singer wiring. Also I'm thinking that it would be easier/safer to to take the wires off the back of the terminal posts and "graft" the light wire to a plug and the motor wires to a plug and then use a motor block. Of course I don't know anything about Italian wiring.
I would think that somewhere in Italy that there would be an "old sewing machine guy" who has repaired and serviced old machines and has some old bits and bobs that could be used. Actually, here in the US, dealers are more interested in selling
new machines than they are keeping these old ones running.
just a thought, there should be more Necchi 'experts' in Italy than there are in the US/Canada
Janey - Neat people never make the exciting discoveries I do.