I'm not sure that the eye 'glow' is a particle. It may actually be part of the model. However, I suck at model stuff so I'm not knowledgeable enough to help you. There are others who are good at this sort of stuff but getting an answer in this forum is becoming increasingly unlikely. You may try asking your question in Discord.
Edit: Found this link showing how it's done for Source Filmmaker. Appears to be a particle labeled 'bot_eye_glow'. Here's a link:
https://steamcommunity.com/sharedfil.../?id=746191556
I don't know how you'd translate that into a plugin.