This is a suction cup holder to mount a TP Link CPE210 or CPE510 to a window or other flat surfaces.
I used suction cups with 40mm diameter and a 10mm long M4 stud on the backside with a knurled nut. You can source them via internet quite easy.
I do not recommend to use PLA, as it most likely won't withstand the weather conditions outside. Better use PETG or any other tougher material, that holds up to rain and direct sunlight.