Customer service at Tristar told me they are out right now, but will have 10 round mags in stock at the end of the month. AFAIK, Tristar is the only place you can buy 10 round mags. Also, 10 rounds is the max size mag for now.

Call Tristar Phone: (816) 421-1400

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Hi Brian, Call Tristar Phone: (816) 421-1400

I have searched to no avail Brian. (No Luck) You can see if TriStar Arms has any recommendations here : tristararms.com/contact-us/