Contact Robert Vivas at the e-mail address on his website. Link below. I was last in touch with him last fall. He should have records for that time period, at least if the gun was sold through the NYPD Equipment Bureau. He'll need the serial number of the gun.
If that doesn't work, for info via the shield number, you'd have to go through NYPD via a Freedom of Information Act request, and I don't know whether just having the shield number is enough for that; from all I've heard, they don't part with info about individual officers voluntarily unless you can prove that you are a family member.

NYPD Small Arms Page - Issue Guns & Markings - RM Vivas