Cisco removed most firmware downloads for these older EOL phones from public access, so without a support contract it can be difficult to obtain the actual firmware package directly from them.
However, nothing is stopping you from doing a Google search for:
cisco-ip-phone-7940-7960-sccp-sip-firmware-v8.1.2.sr2-v3.8.12
and you may be able to find a download link from community or archive sources.