SoCal here too. A few years ago, the local nursery was giving out milkweed for people to plant in their gardens. We did that, then a couple of years later they apologized because they had given out the wrong type of milkweed, and it was actually worse than not having it at all. Pretty fucked up. Anyway, we used to see a ton of them come through, the last couple of years it seems like I see a couple dozen or so at best.
I’m in northern OC. Along the route. I found this nursery, https://californianativeplants.com/, out on the Ortega Highway out of San Juan Capistrano and they have fantastic California natives and knowledgeable staff. They aren’t on the list, but they had the correct varieties last time I hit them up. I don’t own stock or anything, I just really like it, even though it’s a bit of a drive for me. They’ve set me straight on several things I had been doing wrong.