Just a thought, but for something a little different and presuming that you can see your gear selector position on the dash display you could add a custom shift boot to your new shift knob.
I've seen this done with a number of other AT cars (not NSXs) and it looks quite nice. Detach the dash trim panel and the shift knob. Drop a boot over the AT selector shaft and reinstall the dash trim sandwitching the boot between the dash trim and the AT shifter panel. Reinstall the shift knob and thats it!
It wouldn't be too difficult and would make for a manual transmission appearance.