One of the best ways to get organic polymer is a moschops or direbear. A moschops can be leveled into organic polymer harvesting. Once you have it to a good amount (250%-300%) go to an area populated by penguins. Kill them, and whistle the moschops to attack their corpses. Do NOT ride it instead of whistling it. It harvests way more polymer by itself. Direbears harvest a lot of polymer from polymer plants. They are a better alternative if you live on a map with organic polymer plants.