How to mount GoPro between front seats?

Title basically says it. Specifically a Mini Cooper S F56, without a sunroof, otherwise I'd be sticking the GoPro to the glass roof.

So far I've been jerry rigging it to the co-driver seat headrest, but ideally I'd like a cross-bar which mounts to both the driver and co-driver headrest metal bars, and provides a stable horizontal mount for the GoPro.