These may not be covered securities but the wage reporting requirements were the same for those years.

Before venturing to use public websites to determine your client's cost basis, you should ascertain what kind of options those are.  Statutory options are treated very differently from NQSO.

It's best to go back to the returns filed for those years as well as the related W-2s, comp breakdown, and stock options documents from that time.  Historical trading prices do not establish basis.  What was, in fact, previously reported as your client's gross income does and the burden of proof is on the taxpayer.