The easiest for you is to contact our friend Mr Ritty 012707719. You can visit him in his office by the Riverfront. He can help you arrange both shared taxis, that should be about $10, or private taxis, that should be from $70. The trip should normally take 2-3 hours. The taxi will take you to Poy Jopon. From there you take one of the small speedboats to the Island. When you share the boat with others the normal price is 5000 Riel or $5 for your own boat.