I have recently found a light gun for the Commodore 64, it was made by Cheetah Marketing and was bundled in the Light Fantastic pack, and was also available as part of a standalone game pack
It seems the different light guns available for the Commodore 64 were all compatible with each other
Side profiles
Cheetah Marketing and Defender 64 logos
Down the barrel to the light sensor
The rear of the gun
The Atari standard plug
?OVERFLOW ERROR