Take a look at Quadlock for your bike.
The problem is the clamp itself on the stupidly expensive Givi mount / case I got due to my bars. I might be able to mount it on the support bar but it doesn't fit on the main bar due to the support one plus the distance between main bar and headstock bolt thing.
Image below shows the support / cross bar that stops a clamp mount from working on the main bar. The phone mount did come with some rubber padding for wrapping around bars / mirrors (if mirrors mount on the bars, mine don't) so I might be able to use that to pad out the cross bar and make it fit. Short of doing that, I think the next best option is to get a new set of bars without the cross tie thing but that seems a little drastic to resolve a minor issue of mounting my phone. I don't need the phone to be mounted, it's just useful to have a quick glance at when going on an unknown route as audio instructions aren't always too clear.
I'll have some free time over Xmas and new year so will see what I can do with what I have.
E: that being said, the one you mention does look so much simpler and nicer to use. My phone (OnePlus 7T) isn't IP rated or whatever it's called but that's down to OnePlus not wanting to pay for it, generally it should be fine getting wet. I shall look into those mounts too, does look nice and slim and easy to use, mounting clamp looks quite slim too so could be an option. Thanks.