1/35 German spare barrel carriers

[Sairou]

I'm trying to track down some spare parts for this thing, which is a case for spare MG barrels commonly carried by Wehrmacht infantrymen. I'm somewhat baffled how I have so few in my spares, and how they seem to be uncommon in terms of aftermarket, considering one basic infantry squad would carry up to three of these at a time.

Does anyone know where I could find these? I have two Tamiya versions off their machine gun crew sprue, and could probably make copies of these, or make my own out of tube, but other than buying the Miniart machine gun set *just* for the two cases, I have no idea how to solve this problem.