The way for finding a gap is to search the web and read recent articles in which authors suggest what further research needs to be done. And then selct one that interest you, or you feel passionate about, and for which you have access to get primary data.
Have a nice day
Leaning and Teaching Fellow (Retd)
The University of Bolton, UK
Chief Advisor, Promentor-consulting
You can choose the following topics in HR.
Industrialization in India, evolution of Labour Laws legislation and Administration.
Labour Welfare Legislations in India.
Women Employment in the past and present.
Wages and Salary Legislation s/Policy before Independence and after and at Present. etc
LL.HR & IR Consultant