My dog loves to chase and collect a ball. But then runs off with it. I've no difficulty calling her back but it is usually without the ball. We have lost so many! Tennis balls soon take on the colour of the surroundings, and even prime colour balls get lost in long grass. I see there is an app which can find golf balls but only because they are white - can anyone recommend a white (tennis-sized) ball? Or a ball that will flash or beep on command?