That's what I want to know as well. This github[0] mentions the sensor as a standalone item, and this appears to be the manufacturer[1]. This[2] is the closest I could find for purchase (24GHz, as opposed to Soli's 60GHz, and nearly 300 bucks to boot).
[0] https://github.com/simonwsw/deep-soli
[1] https://www.infineon.com/cms/en/product/promopages/60GHz/
[2] https://www.avnet.com/shop/emea/products/infineon/demodistan...