I needed to mount a temperature sensor outside and made a cover for it.
with the teardrop shape you can face the perforation on the side toward it and get better 

I printed it in TPE-83A witch makes it relatively easy to remove the sensor when you need to change the battery.

If you want to make a larger one for a stiff material I recommend changing the diameter of the initial sketch in the f3d file.
All relevant files are available.