Raspberry pi 4 case attached to a waveshare 5inch screen. 

I used to have this at the car with a USB carplay adapter to make use of carplay features in a non-carplay car. I originally printed this in pla but I wouldn't recommend since it ended up melting a bit when it was stored in the car, other materials as ABS or any that could resist temperatures. you'll need a flat HDMI cable to connect the screen to the raspberry in a small size, you can see it in the image, I found those in aliexpress.

Note that the back doesn't have anything for mounting it to the dash, that's because I used a few magnets and it sticked in place, you might need to modify the back and add a few holes or whatever you need for support.