https://www.armsunlimited.com/Colt-AR15-M16-M4-20-round-USGI-Aluminum-Magazine-p/sp62103.htm
Or
https://www.midwayusa.com/product/132999/ar-stoner-magazine-ar-15-223-remington-556x45mm-300-aac-blackout-with-anti-tilt-follower-stainless-steel
It looks like you have an inventory of pretty cheap mags ($12 or so), would be nice to get some of these