Taking up slack in RSX shifter?

I've had the Revo shifter in my type s for a few months now but there is some back and fourth slack that wasn't there before. I've put washers between the upper shifter link and cotter pin but it's still wiggling.

It wiggles enough that if I don't look down, I've mistaken the car to be in neutral when it was actually in gear. :down:

Is there any other solution to this? This shifter is a lot easier to work with than the factory shifter and honestly, the play is something I can deal with but if there's a way to reduce it, I'm all ears.

Thanks for any help or suggestions!