You will probably not find any powder that is entirely free of Pb and Cd, but if it is any consolation, a 2018 investigation into 144 products consisting of cocoa powder, dark chocolate, milk chocolate, and

cocoa nibs showed that the heavy metal contamination for all products remained below the recognized safety levels: "The Cd and Pb levels observed for specific products do not present a safety concern based on comparison to the JECFA 2013 cadmium assessment and the FDA guidance for lead in candy likely to be consumed by small children (FAO/WHO 2013, FDA 2006a)." For Cd, there was a regional difference, with Cacao from West Africa having lower concentrations than from South America, but for Pb there was no such geographical gradient.

That information will probably not help you very much, because manufacturers tend to blend different cacaos from different regions.