I've been wanting to design a nice enclosure for the Bat Listener kit which I sell on-line and recently I found the time to build and test a prototype.
I used laser-cut plywood and the slots and t-nut holder method, as shown here.
I built in some additional segments to hold the battery and keep the circuit board in place.
Hee are photos and design plans for it. You can buy this, either on its own or bundled with the bat listener electronic kit here.
The ultrasonic receiver pokes out of the unit.
The variable resistor and switch are fed through to the front. The battery can be replaced by unscrewing the front panel.
Everything fits within the case, in its own segment. The loudspeaker is held without any glue.
Here is the bat listener case design as a pdf:
The .dxf files can be downloaded from this link to cut on your own laser cutter.
Instructions for putting together the enclosure are here: