You first need a place that will ship to Calufornia.
Here is a list of places that will ship ammo to California:
https://www.calguns.net/calgunforum/...40&postcount=1
Then, you need that place to have inventory to sell.
Check with the places above and see what you can find available.
Then you need a local dealer to accept the ammo for you and transfer it to you.