I couldn't find anything that I really liked, so I came up with this no-drill solution. It's a generic stick-on mic holder, stuck to a metal plate (like you would attach to your phone) and on to the magnetic vent mount. I used the large metal plate that was provided with the mount but I had to use 3m adhesive. The thin stuff on the metal plate didn't work because the plastic mic holder is not perfectly flat in back and I didn't trust the adhesive that came on the mic holder.
This is the mount-
https://www.amazon.com/gp/product/B078MJ9SWP/?tag=wranglerorg-20
This is the mount-
https://www.amazon.com/gp/product/B078MJ9SWP/?tag=wranglerorg-20