A basic GPS Antenna support.  I made it to add a larger GPS antenna externally to Alley Cat's case for the Lilygo T-beam.

The round part fits into the hole for the head of the M3 screw meant to hold the case parts together. Just use a longer screw, instead of the M3x8. I used M3x14.

If you haven't printed Alley Cat's case yet, you can use your slicer of choice to place put a hole to feed the antenna cable and connector through. If you already have a case you could carefully drill a 5-6mm hole for the antenna cable and connector. (Be sure to take the Lilygo T-beam board out before doing this.)

The antenna support has a couple clips that help hold the antenna in. My antenna was 25x25x9 mm with the last 4mm the antenna is a bit smaller, about 24x24.

Probably this could work with another model with suitable mounting holes for an M3 screw. 

These was done relatively quickly in OpenSCAD, somewhat parametric perhaps even readable. 

Changes with V2.
* screw mount. moved and a bit larger
* closer fit for GPS antenna
 
V2 in black was printed with Prusaslicer's fuzzy mode, with the numbers toned down to about 0.1 - 0.2 … interesting look.