Have you tried OXFORD NAV BAG / BAFFALO NAV BAG ? this straps to the yoke itself , and you can see your phone or satnav as clear the dashboard too, i use it sometimes on the GTR when i am not on the GV Cruiser.
Not much room around the bars because anything else will hit the fairing screens when turning and they tend to vibrate like crazy, i never trust it.
Or, buy a SPARE Hyosung steering nut, go to a bike shop, to make a hole in it , and you can look at doing RAM mounts (many variations on Amazon US store, so have try one that fits you)
If not, i usually sometimes also chuck the phone in the bag, and rely on bluetooth earpieces in my helmet.
Welcome to the club and nice ride! – Yes they still make 650s , their latest is the GV650 Pro ABS , the GT650 was last made in 2016-2020 era (no news on revision of the GT250 and GT650 yet)
Keep the GT250R , it’s a nice little rocket! – very rare to find one that clean these days!