There are guaranteed NPCs at mi-go camps, those place are pretty damn dangerous though. Refugee centers also have NPCs and so do Hubs, can’t remember if you can recruit anyone at the center though and you can’t at the Hub. Otherwise you’ll just have to wait for someone to turn up, it might just be chance (or they might just survive longer and I can spot them easier) but I tend to have them turn up after spending time in more openish areas that are out of the way like farms/cabins etc.
Use the computer in the shelters and it will give you a route to the nearest refugee center, Mi-go camps just seem to spawn outside of cities, you’ll know when one is near when you start running across lots of mi-go type enemies (be VERY careful, the higher level mi-go can be really nasty to deal with).
Prototype cyborgs in the labs can be rescued, too, if you have good medical/computer skill, and have either scrambler grenades or a control laptop to disable them safely so you can perform the surgery.