I scratch off dirty, hardened tack from the sides of tape dispensers, form those into tiny booger-sized balls, and put that inside a bushing and push it back into position on the tremolo arm. They will stay reasonably tight for a good while. When the tack starts to creep out onto the sides of the bushing, just scratch them off, ball them up again, put in between the bushing and arm, and done. The only downside to this is that they look like "libag" stuck on the white plastic bushings, but I've been doing this on my Edge Pro trem with lots of success.