My car was missing one of the caps for the wiper arm - so this was quickly modelled after the OEM cap I still had. You'll see some layer lines at the top depending on your printer quality, but a little bit of sanding with a nail file and a couple layers of black paint or plasti-dip and it really cleans up. I'd say within 5-10' you can't tell the difference from OEM even without much post-processing at all, and is far less noticeable than missing the caps and showing potentially rusty nuts holding the wipers on.

I printed this in a black PETG that will probably not endure the elements unless the plasti-dip I used on it helps to protect it, and also attempted a print in TPU which came out looking pretty good with no post-processing but it may not survive the heat. These buttons are typically tucked slightly under the hood so they may not get direct UV.

You may need to print with supports but it doesn't affect anything since you will not see any of the attach points and any imperfections in cleanup may also help with snugness.

In the uploaded photo you can see a comparison of the raw print (right, not installed) and the slightly sanded and plasti-dipped print (left, installed).

Enjoy!