I think all the schematics come from slicing/underworld trading, at least I haven't seen another source so far.
Would be nice to have more detail, like which schematics are aquired where/how, like specific crew skill mission ranges.
I've gotten all my schematics from either the GTN, running UT missions or guild members. The missions give ranges when you run them, so a UT mission for range 41-48 has the possibility to bring back one of the level 43 schematics or one of the level 47 schematics. I don't remember all the exact ranges, but maybe when I get a chance I can add that in to the original post. Really, it's easier to just look at the title of your UT missions and see what range they cover, determine what piece you're missing and run the appropriate mission. Much easier than writing anything down from a list we can provide here, or tabbing out to double-check.
I have a ton of the Aspiring Knights schems, in fact, I'm just banking them waiting for the guild bank to open up (once we can have the neutral gtn on our ships, it's not so bad to learn a schematic for the opposing faction!). For some reason, if it's a class specific schematic, the other side gets them too when running UT missions.
I'd run UT missions in the range you're looking for, check the GTN, and be sure to check the Neutral GTN in Nar Shadda every now and then. It's usually a bit empty on my server, but just the other day I found two headgear schematics I was missing for cheap there.