You won't find it because MGLs does NOT allow for this! 1998 law made NO EXCEPTIONS for LEOs at all.
AGENCIES can purchase whatever from wherever, so some LEOs get their PD to order it and then the PD does a "private transfer" to the LEO. I am in no way going to address the legality of this sort of thing (it WOULD violate Fed Law if the FET was not paid and it was immediately transfered to an officer)!
The AG Regs (CMR probably quoted or referenced here on Gun Laws or LEO Bubbas sub-forums, suggest use Advanced Search and you might find it) DO have an exemption for LEOs.
Therefore, any gun on the EOPS List (e.g. Glocks) can be privately ordered by a LEO, But if it is NOT on the EOPS List, it is supposed to be "untouchable" by an individual LEO.
HTH