It sounds like Sulfate of Potassium might be a good option. No chlorine and it is produced from the Great Salt Lake in Utah.
https://www.amazon.com/Pound-Potassium-Sulfate-Potash-Organic/dp/B004JD6MGK
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https://www.amazon.com/Pound-Potassium-Sulfate-Potash-Organic/dp/B004JD6MGK
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