Finding a Water Tester Kit?

For a science project I am testing 3 bodies of water, The Rappahannock River, The Potomic River, The Chespeake Bay adn for my control variable I will be testing purified drinking water. I am looking for a water tester kit under 30$ that tests up to 12 times adn tests for nitrogen adn phosphorus. I just want a straight forward easy to use kit! Thanks! 10 points to best answer!!!