When you get a Tesla, you want a BlackVue to protect it day and night. In this video, YouTuber T Ma explains how he powered the BlackVue in his Tesla Model S.
Check out this video to see the trick.
Of course a word of caution is necessary here before you decide to do this, as with this method you are on your own. Indeed, if you cut the power cable you will lose the fuse integrated in the 12V accessory power male connector of the dashcam.