AR-Stoner Mag AR-15 223 Remington 30-Round Curved Body Anti Tilt
midway has some mags -- only thing is they have a limit of 2 per order.
might be worth it if you buying parts from them to toss a couple in the cart.
these are made by ASC/C-products
this looks to be the only ar-15 mag in stock right now @ midway.