I've replicated an Amplivox 13100. It's intended for Type P and Q oxygen Mask, but It can be used to with the type H mask, I believe.
I've tried to be so accurate as I could. It has the exact size and shape than the original one. The shell is divided, so it would be possible to insert a working microphone. And the switch it's movable. Some small screws are needed to secure close the shell and to attach the switch.
Amplivox13100_AccurateXXXXX.stl -> Parts to exact replicate the microphone.
Amplivox13100_EasyPrintBody and Amplivox13100_SpacerInsert.stl (Red bit in pictures) -> To be the most accurate possible but make printing easier, I did this tiny spacer as a separated part.
I recomend high resolution printing, 0.1mm or less (better) and 100% infill to make it durable. For top quality, print it in resin. Only minimum sanding to clean/fit parts and if you use black color material, you wouldn't need to paint it.