Arkon sell 'waterproof zip in' motorcycle phone cases for various phones with a clear front and ram ball on the back and a cable entry point.
I bought one and used in conjuction with a short ram arm and ram mirror base mount and a charging lead, the case is padded inside to prevent damage to auto focus phone camera's too. When leaving the bike unattended remove your fully charged phone and pocket it. Remove case and ram arm in seconds and pop it in top box. The mirror base ram ball could also be used for camera mount too.
The case 'window' is similar to a tank bag and can operate the touch screen without removing phone from case, (without gloves on when stopped). You can see phone for navigation and angle it, portrait/landscape, I use my Nav 6 for route planning and then Google maps on phone for short diversions to something unplanned for.
My S20 phone remains secure, dry and dust free, camera not damaged through vibration, always fully charged, visible when riding, close to TFT so always connects.
Incidentally I've recently discovered a battery bank can power the Packtalk whilst it's being used ! on long journeys using nav, music from phone, talking to passenger or Pack in DMC the battery wouldn't last a whole day. Just put battery bank in top pocket on jacket, short lead to charging port on underside of headset, plug in which will turn Packtalk off but it can then be switched back on again and run for days if need be.
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