You can build your own if you are patient enough, though. In my current game I took a three star general and attacked the HRE. They then threw massive counter-attack after counter-attack against him. By the time they were winded he had gained a few stars from experience, plus he was now some kind of field defense expert that gives him 3 more stars on defense. Took him out on a few risky attacks and now he also gets two stars when he attacks. Made him the gov of some province that gives one more star (even though his acumen is kinda low.) Left him at 9 stars defense, 8 stars attack.