I send you the scale that we have validated and published in 2013 in health care professionals (Registered nurses (RNs) and nursing students, radiology technicians (RTs) and radiology technician students). I hope it will be useful.
Cadorin L, Bortoluzzi G, Palese A. 2013. The Self-Rating Scale of Self-Directed Learning (SRSSDL): a factor analysis of the Italian version. Nurse Educ Today 33(12):1511-1516.