Memoji/Animoji transparent background video

**TL;DR: I want to get a Memoji video with a transparent background.** When I record a Memoji video in Messages, the video clearly has no background (transparent) as switching between light/dark mode (in iOS 13) switches the background of the video in Messages and in the camera roll between black and white. However, if I save the Memoji video and airdrop or email it to my Mac and load it into a video editing software (final cut pro) or into photoshop, the video has a black background. I need the transparent background version of the video as I want to use it for a personal website I'm building that will have a light/dark mode where the background of the website changes colour behind the Memoji. Is there any way for me to get a Memoji video file with the transparent background? If not, does anyone have any suggestions on how I could best edit out the black background? I have tried after effects but the rotoscoping didn't work perfectly, and I don't want to have to cut it out frame by frame in photoshop as the video is ~10 seconds long. Appreciate the help!