I have a similar squeak. And I hear that these are quite often caused by the ball joint. In my case, I had a good brake and suspension shop take a look while it was in for brake work. They said my ball joint was silent, but the tie rod end was squeaking. So I'm going to swap that out this winter. Another possible source in your case may be poly bushings, if you have em. They often squeak if not greased.
If its your ball joint, you might want to look into just swapping out your lower A arms. At least that's what others tell me. Because you need to get the ball joint pressed out, and the new one pressed back in.