Mountain Rose Herbs is selling some - https://www.mountainroseherbs.com/products/palo-santo-essential-oil...
Sage Goddess has only variations of it in combination with other ingredients. I like Sage Goddess but I have never ordered from them so I have no idea how authentic their products are. https://www.sagegoddess.com/
Maybe you could try Etsy? There are a lot of occult vendors.