Dear Giulia, 

perhaps you may consider the  Pathological Narcissism Inventory by Pincus and collaborators (2009, 2013), a 52 items self-report which includes scales on both Narcissistic Grandiosity and Narcissistic Vulnerability. Recently, Andrea Fossati and colleagues (2014) have published an article where this measure was applied in an Italian sample. I think you may directly ask Andrea for the Italian version of this measure and... be confident about results of your research, my own research on IAD and PIU suggests that you will find significant associations between NPD scales and IAD scores.  

All best wishes,

Adriano

References

Fossati, A., Feeney, J., Pincus, A., Borroni, S., & Maffei, C. (2014). The structure of pathological narcissism and its relationship with adult attachment styles: A study of Italian nonclinical and clinical adult participants. Psychoanalytic Psychology. doi: 10.1037/a0037175.

Pincus, A. L., Ansell, E. B., Pimentel, C. A., Cain, N. M., Wright, A. G. C., & Levy, K. N. (2009). The initial construction and validation of the Pathological Narcissism Inventory. Psychological Assessment, 21, 365-379.

Pincus, A. L. (2013). The Pathological Narcissism Inventory. In J. Ogrodniczuk (Ed.), Understanding and treating pathological narcissism. Washington, DC: American Psychological Association.

I would also recommend the Pathological Narcissism Inventory (PNI) as it has shown adequate psychometric properties in several different cultures (American, Italian, Chinese, Croatian) and it assesses both grandiose and vulnerable expressions of pathological narcissism. 

Another self-report measure you might consider is the Five-Factor Narcissism Inventory (FFNI) developed from a FFM perspective (Glover et al. 2012). It is quite comprehensive but rather long (consisting of 147 items), so the choice between these two instruments depends also on the length of other measures planned to be used in your study. 

Best,

Nenad

Glover N, Miller JD, Lynam DR, Crego C, Widiger TA. The five-factor narcissism inventory: a five-factor measure of narcissistic personality traits. J Pers Assess 2012; 94(5):500-12.

Miller JD1, Gentile B, Campbell WK. A test of the construct validity of the Five-Factor Narcissism Inventory. J Pers Assess 2013; 95(4):377-87.