This holder is designed and tested by me.
It has a firm grip on the pager but it is easy to take out. The clip of my pager broke so I don't know for sure if one with a clip will fit but it should according to my estimation.
It is better to print in a material that can withstand some temperature as the preferred location is the top of the dashboard (pic will follow soon).
Picture is printed in DASFILAMENT PETG Beige with 0.2mm LH on Prusa Mini+
The author hasn't provided the model origin yet.