Dotted around the wastelands, there are various drug sellers. Not sure of their complete lists, but the interesting products they sell are:
Poison Resist Potion
Xray Resist Potion
Energy Resist Potion
Fire Resist Potion
Force Resist Potion
Antishock
Advanced Antishock
Concentrated Antishock
Antidote
Advanced Antidote
Concentrated Antidote
Damageblocker
Advanced Damageblocker
Concentrated Damageblocker
Stealthbreaker
Advanced Stealthbreaker
Concentrated Stealthbreaker
Unfortunatley, I don't know many locations for these guys.
Crest Village has one, in the GR building, along the long corridor.
Theres one in B08 too, in some broken down builldings on the road running west.
Feel free to add others, my memory is a touch blank right now.