How can I convince a little girl's parents to buy a Betta fish?

This little 4 year old girl I know, wants a betta. How do I convince her parents? I made my own Betta Magazine convincing them, brochure and I will give it to to them later when I go over. And I am going to talk to them when I go there. But quick! I need ideas! I am going REALLY REALLY SOON!