WHERE TO BUY AMMUNITION FOR TARGET SHOOTING NO FURTHER A MYSTERY

MoCo Acquired a rifle that normally takes AICS mags. It arrived w/ one particular PMAG10 AC. Thats quite long if working with susceptible (TIL AICS mags are one stack.) I desire to purchase a handful of 5rd versions. Wanting online I recognize magpul has new 'Sig Cross' variations w/ a follower that has just a little feed lip within the front that