For core.stl, switch filament from white to black after the first 16mm.
Print led.stl hollow and spiralized, with a translucent filament. I got these results with a .6mm nozzle - because I misplaced my .3mm.
Print antenna.stl with a brim and trim it partially. The flexible brim keeps it from falling out of the casing. Alternatively, glue it in place.
I used a thin paint that was easy to brush around for the padding space between the buttons of casing.stl.
The assembly includes a pilot hole intended for an M3 fastener, which may be used to attach a belt clip.