For those who are looking for some inspiration: I found a cheap yet practical shock-/waterproof case. Available in three colours (beige, black orange) in the Geek/Wish store.
The plastic box measures 12,5 x 7,5 x 3,5 mm, is equipped with a rubber seal and fitted with an inner lining.
With some minor adaptations it’s ideal for the AudioMoth. The inner lining consists of foam in which the shape of the AudioMoth can be easily cut out. For the fixation of the membrane I was inspired by the Aurita design and used a PVC shoulder washer. After drilling a hole just above the mic I enlarged it until the washer fits tightly.
Since the materials (plastic vs PVC) are difficult to glue I used butyl tape to attach the shoulder washer.
Butyl is an excellent watertight sealant and has high strength adhesive properties but can be removed without destroying the parts.
The membrane, standard cling film (10 micron), is mounted on top of the washer. In order to prevent damage by the sharp edges there there is an O-ring on top. The second O-ring stretches the membrane over the first one and provides extra protection against water ingress.
Foam tape on the backside of the lid prevents the shoulder washer from touching the Audiomoth when closing and keeps the device tight in place.
I also provide a silicagel packet to prevent condensation on the membrane and as extra safety in case of the membrane is compromised. It is advised to check the membrane after each battery change because the cling film degrades due to weather conditions. Also the O-rings suffer from UV-degradation after a time so be sure to check their condition as well.
The box has two ‘eyelets’, very convenient to attach the box.
The plastic is partly translucent so you can check the status from outside.
Camo-tape when 'stealth mode' is required
The box costs 2€ and together with the other stuff you have an excellent enclosure for less than 5€ and 15 minutes crafting.