Bigtexoutdoors.com has the Medium Coyote Tan Pmag gen 3 windowed which I believe is the same one that the USMC adopted recently for $15.99 each.
https://www.bigtexoutdoors.com/product/pmag-30-ar-m4-gen-m3-window-5-56x45mm-nato/?attribute_pa_color=mct-medium-coyote-tan
If you use promo code...