The amount of Space Invaders clones, bootlegs, and variants is so large that they are STILL being discovered. You see these hunts for specific versions quite often, and often times they are fruitless. You might have very well played a bootleg or variant that only had a couple dozen units produced.
If you are searching for them in Mame though, then just manuall go through the clones for 1987, 1979, and 1980, and if it is in there, then you will find it.