Lost share certificate

As per the concerned matter you've explained above let me inform you that from November 15, 2020 an individual could get copy of the First Information Report (i.e. FIR) registered before police station or special units in Tamil Nadu, merely by visiting the official website of the TN police as all FIR's are now available online. Any individual can access these FIRs, except sensitive cases.
Although, reports made to DVAC, CBI, NCB & NIA won't be able to access by anyone, except parties involved.

Therefore, access the official website and register yourself up there, then add details like PS (police station) and dates (when FIR was made), according to which FIR reports will be available from which you can select the report you're looking for and get a printout for the same.

Once, the FIR has been obtained you may approach the registrar with the copy of the same.
I'm leaving the link for TAMIL NADU POLICE official website for your assistance -
https://eservices.tnpolice.gov.in/CCTNSNICSDC/CCTNSContact

However, if you're unable to get the FIR online you should approach the police officials (of the particular PS), in order to find an alternative method for doing the same.

Hope It Helps!

Regards
Kevin M. Paul