Most things are readily available already.While this reply probably belongs in the thread of making fine powder, I am too lazy to go back to it and post it there. Maybe the Moderators will move it, or just delete it.
Why not take a water jet cutter, and with a slow feed rate, produce the desired size powder to their requirements. Particle size will be dictated by the feed rate of the Sterling bar stock. Perhaps this is how the original posters process is achieved, leaving the 99.99% waste, which of course is just folly, as it will be ultimately consumed for product. A water jet facility would probably be willing to try it for a fee. The cleanup before and after, will be the most expensive component. Should somebody on this forum actually need atomized product.
This was for special applications.
But I'm not entirely sure the OPs intention was to sell much of the physical powder anyway.