What else have you tried as far as getting him to drink? The problem with waterfalls is less that they might not drink from them, and more that unless you clean it and change the water a couple of times a day bacteria can thrive and multiply, making it unsafe to drink from. Added to that bugs falling in and drowning, debris from plants etc and it's a very effective petri dish. You are right that he's only likely to drink moving water, but that can be achieved more safely using something like regular mistings or a dripper (which doesn't need to be a purchased one, just a cup with a pinhole in the bottom works just as well).