I actually use 10 rounders in my Sport 2 even not being in CA, just easier when shooting off a bench and helps me watch my ammo count when I have to keep changing mags lol. And they are a little lighter to carry around.
I went with the “factory” Pmags (I assume a CA compliant AR comes with at least one?) and they seem to be available online at multiple sites. I cant say if there are any restrictions shipping them to CA, am sure those sites would list them if they did exist.