ToME: the Tales of Maj'Eyal

I recently unlocked tinkers for AoA, and I was wondering if it is possible to find or otherwise replace the default implants on the default campaign, as there aren't any in shops and I haven't seen one drop yet.

There's exactly one shop that sells steamtech stuff in the main campaign, by default (there's an addon or two that adds more, I think), though it takes some effort to get it to show up and non-tinker classes have to invest some resources to start using it. Seek the teacher, yadda yadda. I'm about half the sure the chance is guaranteed if Embers if active, but it's possible to mess up or miss the requirement and effectively miss out on tinkers entirely for that run.

That said, once you've got the shop open, and if you're willing to pay the price, steamtech stuff (schematics, steam weapons, etc.) should start generating, and should generate by default (though they seem do to be somewhat less common than other inscriptions/kit/etc.) if you happen to start as a steam using class. So yeah, you can replace the default implants, it just may take a zone or three for it to have a decent chance of happening.

I wish there was a way to unlock it without saving a specific escort. Well, I wish that were true of all escort categories in general. EoR's system for handling unlockable categories is better overall because you don't have to rely on RNG or scumming to get what you need for your build.

That being said, you can unlock the Physics and Chemisty trees for 1 category point (total) after saving a tinker escort, asking where they learned their craft, and completing a small mid-tier dungeon.