Starlight is something you have to walk back to Sector 5
There's a man walking around that will trade you one of the pharmacy things for Starlight
I /think/ I also had another way to get it but it's been a while since I overworked that part.
There's a Nightmare thread btw where you can ask, I usually check that every day
Edit: Oh yes I remember. Starlight isn't actually called Starlight but the street name for a drug. Iirc some NPC tips you of to the name