Well, I was thinking in two things: 1. You put items on your brahmin and any NPC could come and force a dialog with you asking to buy X item with Y price, then you could awnser with "yes", "[barter X] I'll sell it for Y caps", "[barter 2X] I'll sell it for 2Y caps" and "no" 2. The same but with randomly spawned NPCs done for that thing. Alternatly you could just put the items in your Brahmin and people come near you, pay you caps and remove that item, and depending on your barter level you get more or less caps. Also i didn't know that command existed, so it makes it easier to at least roleplay it.