Seriously man, its time for some detective work. You can't rely on the police for this kind of stuff.
You need to gather up some buddies for the next week, and do some surveillance. Park your car facing the other direction and wait. I wished I lived closer to you, I'd go spend the night out there watching.
I noticed, the damage looks to be on the drivers side facing the street. Do you have kids living across the street? They could be shooting it with a pellet gun. Make the police go over and investigate that.
You may not be able to get any money out of a 13 year old kid, but you can nail his parents. They should be watching their children anyway.
Seriously with the frequency this is happening, i would be staying up all night waiting for something to happen.
Another option is, you have a computer. Hook up a webcam. Can you see the car from the street? If so, you may be able to get at least a few still images of them.