Ooh, yeah, that one was a hard one for me too. I don't remember the exact locations, but be sure to check all of No Man's Landing, Urchin's Grotto and um, the place with the Great Engine clock? I forgot the name of the last one.
There should be a topic for questions like this somewhere. I don't remember what it is, and I don't have time to check, but @moderators, if you can direct @Mr_W1 there?