These will only be offered by a subset of NPCs.
NPCs that can offer Trade Updates:
Inventory item traders (eg Food Merchant, Arms Dealer, Recruitment Officer or Black Marketeer).
License broker
Mechanic
Police Chief
Ship Dealer (unconfirmed)
Specialist
Non-hirable station crew (they are working on the station) - typically found on Administration platforms (ie Defense Officer, Engineer, Manager).
NPCs that never offer Trade Updates:
Architect (even if they are working on plot-rated NPC CVs)
Hirable crew if they are available for hire (ie Defense Officer, Engineer, Manager but NOT Specialists: Specialists will always offer Trade Updates atm (v4b6)).
Your own hired (green as opposed to blue NPCs) crew if on your own station (v4b6 - needs checking)