I thought I would share my case with the community, it is a variation on a theme but it has worked well in the few tests I have done.
The case is a Lock & Lock rectangular 180ml container (HPL805):
The inner foam housing is 2 layers of EFP30 Polyethylene closed cell foam sheets 20mm thickness. One is supporting the AudioMoth the other is cut to fit the AudioMoth inside :
Then over the hole drilled for the microphone I have used Buzzer Waterproof Acoustic Membranes brought on Alibaba:
The box remained watertight under a tap at full strength, focused directly on the acoustic membrane, so I am hoping rain at an angle won't pose too much of an issue. Only thing I am a bit nervous about is the glue holding the membrane, if it will withstand tropical humidity. I will keep everyone updated.