Hello Massimiliano!
I go often on Italian swap meets. Older CB450's are quite rare in Europe, but I have bought a 71' or 72' CB450 last year (and some parts were the same).
I bet you can find most parts in Imola (Mostra Scambio Imola). I go there every year, and there is nothing you can't find, especially if you speak Italian (at which I am not very good)... Also the Mostra scambio Reggio nell Emilia is very nice, and both are very close to Bologna. I also have a 77' Moto Morini 350 that I bought in Imola, and used to be registered in Bologna.
Your CB450 seems like a German model to me (different turn signals and rear light). I think Italian models had the same turn signals. My CB450 is definitely Italian (it had the first licence plate), and it had the standard turn signals and rear light.
Regards from Slovenia.