Picking up the occasional commodity is all well and good, but unlocking some of the engineers still requires combat missions and heists and other activities that pacifist explorers find distasteful.
As already stated, you can buy from Fleet Carriers or get given Odyssey materials directly when meeting another CMDR in person. None of the Odyssey Colonia Engineers require any unlocks via combat, so for you that would be the ideal place to do the engineering required. If not into conflicts, then you only need to modify the suits. Upgrading (preferably from G3-G5) is done via the Pioneer's. There are plenty of missions that do not require conflict that can be used to gather materials. Abandoned settlements are also good. Leave and return if scavs are present or arrive.
If you can buy a G2/3 Artemis/Maverick) suit with night vision (they are plenty out there, if you put the time into looking), then improved battery capacity and extra backpack capacity (not required on a suit once the material gathering is done), then Rosa Dayette is the only engineer needed to be unlocked. She provides both improved battery capacity and extra backpack capacity.
The materials required to unlock the four Colonia Odyssey Engineers are very modest.
Rosa is unlocked by selling a total of 10 cocktail/culinary recipes to Colonia system bartenders. Providing 10 Digital Designs gets the referral to Li Shen (3 referrals are needed).
Eleanor is unlocked by visiting 5 settlements in the Colonia area via APEX. Ensure that you get scanned for the visit to register. Providing 10 manufacturing instructions will have her refer you to Li Shen.
Unlocking Baltanos is by getting friendly with the Colonia Council. Easily done by selling exploration data to a station owned by them. Providing 10 Faction Associates gets the third referral.
The pacifist path is mapped out. Do you have the will to take it?*
Steve 07
* Rather than go through the Odyssey engineer unlocks in the bubble again, I sent my alt CMDR to Colonia to engineer the couple of suits and weapons I wanted done. I took the unlock materials with me, along with a bunch of others. The unlocks were done within a couple of hours of arrival.