I get 9mm and 40 S&W primarily from the range. Lots of shooters do not pick up their brass. I can generally go to the range and find quite a bit of once fired pistol brass on the ground or in a brass bucket. The ground is thick with the stuff after an IDPA match since thousands of rounds are fired and only a handful of shooters stick around to recover their brass. Different ranges, however, have different policies concerning brass, so you should check to see if picking up brass is allowed.
Much of my revolver brass, 44 Mag, 44-40, 45 Colt, 32-20, 357 Mag, and 41 Mag, comes from Starline. I have gotten a good bit of 45 Auto from LEO Brass. I get their RWS or Speer most of the time.