Hello Yan Phaty
Nice to hear from you again.
I'm pretty sure there is some sort of employment center where you can go to in order to get such a document. Have you asked your local "Centro per l’Impiego" (formerly known as "Ufficio di Collocamento") or at "Centro di Iniziativa Locale per l’Occupazione" (CILO)? I'm not really familiar with the Italian labour market system, but after a quick research these look like the addresses to go to.
If they are not responsible for issuing you such a paper, they can probably refer you to the competent office.
Feel free to share with us if this tip helped you to solve your problem or not.