This type of enclosure is built around TTGO T-Beam LoRaWAN GNSS tracker board.

3D print three STL files from this folder: Body, Lid and Face. You may pick some printing advisories on my Thingiverse page.
Files that have:

• no suffix are either universal or best suited for older V02-V07 revisions of the TTGO T-Beam board ;
• -V08 suffix are best suited for revisions V08 (20190423) and V10 (20190612) of the T-Beam ;
• -V11 suffix are best suited for most recent V11 (20191212) revision of this board ;

If you are unable to print the parts by yourself - you may consider to find an appropriate local 3D service provider and place an order with assistance of Treatstock or 3DHubs portals.

At first, insert printed face panel into front rails. Place T-Beam board into the enclosure's main body. Put lid on top of the assembly. Fasten the lid with four 2.5x10 mm screws.

Two variants of main body are available. One is with GoPro mount and another one is without it.

If you, by any reason, keep using your small T-Beam 'stock' 868 MHz antenna - you may think about to 3D print an alternative lid that has a cone 'bumper'.
This little 'feature' may help for the antenna to survive if the device will experience an upside down free fall.
And it looks nicer, isn't it?

You may opt for 0.96" front I2C OLED display panel.
Be aware that average 0.96" OLED does not perform well against sun light.
Two variants of the panel are available:

• the first design is for generic 0.96" OLED ;
• the other one is for TTGO version of the display.