I also found a cheap one, I bought 100 gram of 50% fucoxanthin extract, but I didn't ask the vendor about dosage because it says it's not for consumption, but the ingredients look pretty clean. Another site sells 35% fucox extract and there it says daily dosage is 50 mg twice. It's on a site called badmonkeybotanicals on a webpage about organic-brown-seaweed-extract-powder-fucoidan.