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.
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.
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.
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 box costs 2€ and together with the other stuff you have an excellent enclosure for less than 5€ and 15 minutes crafting.