Just take a 1" thick board about 2 feet long and and use a jigsaw and machine out a slot about 1 foot down the board along one of the edges (slot should be ~1.5 wide by 3" deep and should go all of the way thru the board). Place the slot over the white plastic ball and press down on either end of the board. The slot should clear the shifter but pickup the white ball. Removal is a snap and can be done in less than 5 seconds. Repeat the above steps turning over the short shifter to reinstall the ball.

BTW, nissan sells the 'ball' for $12. The local Infiniti dealership charges over $30 for it.