Helper sprites are always useful and usually the quickest, simplest solutions.
For a event only version, you would be saving the Touch position to a variable On Touch, and comparing that to the current Touch.X position. With the condition Is In Touch, you can use Scroll to X where X is the difference between scrollx (current screen position) and Touch.X-OriginalTouch.X (length of drag). Depending on where scrollx ends up closest to, you can then set the Scroll to X to the appropriate screen On Touch Released. To get things smooth, lerp can be used as well.
But yeah I would definitely recommend just sticking with a helper sprite as long as you are satisfied with the result.