I really like the enclosures from @AlleyCat so I made a version for the RAK19003. 

The Bluetooth antenna is attached to the side. To mount the board and the switch, you’ll need short screws, or you can use the printed screw washers and use screws from the kit and M2x5 screws for the switch (3 pieces of 0.8mm for the board and 2 pieces of 1mm for the switch). The power switch is the same type used in many other similar projects. 2000 mAh 103450 LiPo battery.