Yes, there are commercially available sub-ambient radiative cooling paints or coatings. These paints or coatings are designed to emit thermal radiation at specific wavelengths that allow them to radiate heat to space and achieve sub-ambient temperatures, even under direct sunlight. Some examples include the "Cooling Paint" developed by the research team at Purdue University, and the "Sunlight-Activated Paint" developed by researchers at the University of California, Los Angeles. These products are still under development and may not yet be widely available for commercial use.
Although there are many well performing paint and coatings developed at lab scale, non of them are commercialized yet. Main reasons are the high cost, inability to apply for a larger area, etc. You could find further information in this recent article.
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I recently wrote a research paper on this exact subject.
I would be more than happy to share my findings with you and discuss any questions or thoughts you may have. I believe it could be a valuable resource for your work and research.