A retrofit HID lamp assembly, for use in a non-HID lighting receptacle, to provide HID illumination. The lamp assembly includes (i) a housing of a non-HID lamp assembly, (ii) a base terminal structure coupled with the housing, and compatible with such non-HID lighting receptacle, (iii) a ballast unit in the interior of the housing, (iv) a reflector overlying the ballast unit in the interior of the housing, (v) an HID lamp mounted in the interior of the housing so that light generated by the HID lamp is reflected by the reflector, with the HID lamp being electrically coupled with the ballast unit, and (vi) a lens coupled with the housing. A corresponding fabrication methodology is described. The retrofit HID lamp assembly may be used to retrofit existing lighting installations, such as PAR receptacles in exterior aircraft lighting systems, to cost-efficiently improve the illumination provided by such systems.