I really like the commitment with which you came up with this device. I've not tried it out yet, but am planning to do this.
It's just that I'm struggling to find the air conditioner filter material.
The shop you recommended isn't available in Germany.
So I have to ask you, if you alternatively can use another material. I've found out that aquarium shops sell filter cotton
and filter sponges, but even those are hard to find.

Here is how the mentioned sponge-material looks like


image

Is it applicable or do you know another alternative;
can I even use mere cotton as a filler?