There are many websites and online marketplaces where you can buy natural oil plants online. Some popular options include:

1. Mountain Rose Herbs: This website offers a wide variety of natural oil plants, including essential oils, carrier oils, and infused oils.
2. Plant Therapy: This website offers a wide variety of natural oil plants, including essential oils, carrier oils, and infused oils.
3. Simply Earth: This website offers a wide variety of natural oil plants, including essential oils, carrier oils, and infused oils.
4. Edens Garden: This website offers a wide variety of natural oil plants, including essential oils, carrier oils, and infused oils.
5. Young Living: This website offers a wide variety of natural oil plants, including essential oils, carrier oils, and infused oils.

When you buy natural oil plants online, be sure to read the product description carefully to ensure that the oil is pure, natural and of good quality, check the reviews before purchasing and also look for certifications.