@karolm
You can buy non drug medecine blueprints to the doctor inside the NCR, near the bar, where you get Awareness and Outdoorman perks
@Bad_Lieutenant
Maybe you're trying to buy blueprint to people who are not selling it. I don't remember who's selling close combat and energy weapons blueprints (never use them), but for the others:
- Rondo in NCR for Armors
- Jacob (don't remember the name well) in The Hub old town for Big and Small Guns
- Renesco in New Reno for Drugs
- Dr Jubilee for medecines in the NCR