Waltorious: Keep in mind that you can update a shop's stock by walking away until the shop is completely off your screen, then waiting 24 hours in-game, then returning to the shop. If you're having trouble finding the steam engine you can do that to speed the search along.
Lukier: I didn't know about that and used to travel outside the town, return and then check all stores. Now it will be much faster, thank you very much.
And about the Small Steam Engines price.. 7000 gold? Whooa. Maybe someone knows if there is any chance to find and steal one or two? :)
If it is a shop keeper that either has their store inventory on their person, or in an accessible chest somewhere you can steal it when you know it is in the store's inventory. But other than that I don't think there are any that are just lying around.
DreadMoth: The medical arachnid is great if you're playing a tech character - unlimited free healing which never fails.
Valid point. I never really saw the use for them because I don't really like the arachnids in general (they are too slow mostly) and so didn't use it all that often (because I was able to heal myself well enough).