Some good deals here if you can make use of 1000 kg: https://www.alibaba.com/showroom/price-soy-protein-isolates....

That seems like the right direction, but even for 20 kg bags I don't know how to evaluate Chinese suppliers of bulk foodstuffs

Are there companies who take care of the sourcing + importing + QA for retail veggie protein brands? Some actor in the supply chain just before flavoring is mixed in

Do any of these brands submit to third party testing?