This is a simple pegboard mount for my handheld digital anemometer.
This model is sold under multiple brands and is available for about $16 on Amazon.
The model is designed parametrically in Fusion 360, so you can make a similar but differently dimensioned part very easily. You can download the Fusion 360 file here.
I also have a post on my website discussing the design.
See how it fits here:
These parts are printed with Prusament Galaxy Black PLA.
Here is my Thermometer Mount too.
The peg design is from Make Anything, as shown in this video.
The author hasn't provided the model origin yet.