The BFG one is very clever. Built well and they handle government agency purchasing just fine (or go through a dealer of their products, we have a few here). Just a bandolier, but you CAN secure as shown if you have a moment, which is nice.
A google keyword you are looking for if you want a cheaper, more generic one, is "M4 Bandolier." Lots out there. But a lot are of iffy quality or sourcing. Or are weird. Or cost a lot.
If it's just for resupply in an AS or other situation where admin can live with any old color, I'd put your mind to getting actual surplus. Hell if I can find the proper nomenclature, but it looks like this:
And you see even at retail repacked it's cheap.
May be able to get a triwall of 1,268 of them from 1033 if you participate in that, for little or no cost depending on your state admin.