This ought to get you started:
https://www.ninjette.org/forums/showthread.php?t=75165
It looks as if, at minimum, you'll need to drill a couple of holes in your upper triple. You need a place to mount the riser blocks.
Define "more straight." Do you mean less pulled back when viewed from above, or more horizontal when viewed from the front?
There's also rise and forward/aft placement to consider. The grips aren't going to wind up where they are now. Don't be surprised if you need a longer front brake line and longer cables for the clutch and throttle.
There may be clearance issues with the front fairing/windscreen.
Going to a separate handlebar will raise your hands quite a bit and make an already-upright bike even moreso. This is because the riser blocks will raise the bar, and the bar itself will also add some rise. You may also find that the bar isn't angled the way you like anyway. Depends on the bar you choose, of course.
Another option is Apex clip-ons. These are costly but super-adjustable to suit your preferences.