I really liked the Thing MrBigTong came up with for primer storage. However there's something wrong with his STL and my slicer (Upstudio) just cannot grok it.
So since this Thing is a simple design I just drew one up in Fusion 360.
I did make a couple of small changes. Mostly cosmetic like placing the view slot in the middle of the front face.
Otherwise MrBigTong's idea is super!
Printed with ABS but I'm sure any kind of filament will work.