I also suffer from stupid round limiting laws in CA. I have found my best mags are surplus steel mags that I have fixed to only hold 10 rounds (Yep, worse off than you I am afraid).
I do this by putting a pop rivet in the mag body to stop the follower so it complies with dumb laws.
Hoping (and fighting) for one day when I can drill that pop rivet out, and load them to the 30 they were designed to hold.
The Chinese rebuild kits at Copes are $13.99, and they'll ship them as 'rebuild kits' even to my state.