There should be alternative fuse taps that should fit. I'm surprised that the guy didn't go and have a look. It's easy to swap them over.
Another alternative might be to check if there is an alternate fuse box that can be accessed that has the same supply.
I went with a cam from insta360.com and it’s worked great in my 2023 GLA. Super easy to mount behind the rearview mirror and the app connection is smooth. Parking mode works well too without draining the battery. I didn’t need to hardwire mine – just used the 12V for now and it's been fine. Their site has good info about compatibility and install, which helped me figure things out pretty quickly.