I like the good-old "free" mod of tightening it.
- Pop the white plastic bushings off the whammy bar
- grab some nail polish (clear preferable, or whatever you have :P)
- paint the slots in the whammy bar. (paint the base of the slots, you want to be able to pop the bushings back in after the polish has dried)
Let the nail polish dry, and then pop the bushings back in to the whammy bar.
Enjoy the tightness till you need to do it again.