Back in 2013 I bought a pair of AP Customs 4x4 Shell Carriers. These were available in 4x4, 3x3, and 4 single stack if I remember correctly. Looking online now the closest thing I can find is a holder from Safariland, and the AP Customs are discontinued.
Have these types of Carriers fallen completely out of favor due to Load2 and Load4?
https://www.midwayusa.com/product/1017859884