PhysX component does not show up in the NVIDIA display driver installer with driver versions 280.19 and above

This is by design. Beginning with NVIDIA display driver version 280.19, if the NVIDIA installer detects PhysX previously installed on your system with the same matching Physx version that is included with the updated display driver, the NVIDIA display driver installer will skip the PhysX installation. This also applies if "Custom (Advanced)" is selected in the NVIDIA installer.