I doubt very much that you will find a mag that holds more than 5 in a non military configuration. If you are looking for something used, you live in a great place. The gun shows in SF and Sacramento are huge. And if you wanted an excuse to make a trip, the the giant one in LA is the ticket. If you cant find something at any of these, then you will be hard pressed to find anything at all.
No such thing as a stupid question. What is stupid is not asking it.