Inventors, blacksmiths, junk dealers... and anyone else, if you also have Haggle expertise. (Note that you need a MA of 65 or less to enter tech-based shops.)

Note that a very few schematics are unsellable. Also, learning a schematic will not affect your MA/TA; and you can use learned schematics in conjunction with enough of the right technical manuals (and of course, the necessary ingredients).

Tech manuals can be bought at Tarant University; their cost and weight are fixed, but their TA boost is tied to your IN. Protip: down a potion of IN just before buying the manuals you need, and another before using them. With an IN of 20, each manual is worth 20 tech points in its college; by comparison, with an IN of 10, each manual is worth only half of that, meaning you'll have to buy (and carry) twice as many.