Some time ago there was a discussion of bar end shifters with Oury style grips on upright bars, with a recommendation to cut off the end of the grip. I had difficulty making that method look neat and tidy so I do something a bit different:
First I slide the grip onto the bar, then I tap the end of the grip repeatedly until the end of the bar cuts into the end of the grip. I keep tapping until the the end of the grip is completely cut through, and remove the resulting rubber plug.
I then figure out the desired orientation of the shifter, and mentally aligned the cable exit with one of the longitudinal grooves in the grip.
Next, I use a coarse small round file to cut a groove of sufficient depth into the small flange on the end of the grip to allow the shifter cable housing to enter the shifter without kinking.
Lastly, I use a suitable twine to wrap and tie the shifter housing to the grip and finish it off with a bit of shellac.
See attached pic.