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THere aren't any publicly advertised US based companies that will ship to CA because, well, shipping spores to California is illegal. Possesing the spores is not illegal until you try to grow them. However, whoever is shipping the sproes to you CAN get in big trouble sending them to you because the "transport" of certain mushroom spores is illegal. Its just not worth it to them for 20 bucks.
International companies on the otherhand, may be willing to ship to California because prosecuting an international company in US court for a small time spore transaction is exceptionnally unlikely. Diplomacy laws make prosecuting one of these companies more trouble than its worth.
This is an academic discussion only.