Ok, I managed to find 2 particle files, responsible for full Visual FX effect for tesla in L4D1.
Since, Silvers doesn't like to include downloadable content in plugin,
I'll just post them here.
Also, plugin should be modified in this way:
DispatchKeyValue(entity, "effect_name", PARTICLE_ELMOS);
DispatchKeyValue(entity, "effect_name", PARTICLE_TESLA2);
and you will have something like stars around tesla mutant in fresh L4D1,
but if you add 2 files from archive you will get this: