It is possible, i've been meaning to get one but have forgotten exactly where it is. I know that there's one on top of a building in San Fierro. If you do the airplane races in Las Venturas, one of the races will be to fly this chopper around the city. You'll be able to see where it takes off from there, or you can just fly around san fierro until you find it, or you can get a lot of stars, shoot one down, and push it into your garage. Your choice.