The "Vibration Amplitude" is only 0.8 G for the 310-101. That's not a lot.
For a diameter of 12mm, there are motors with 1.7G: http://www.precisionmicrodrives.com/vibrating-vibrator-vibration-motors/pancake-shaftless-coin-vibration-motors
You could search for "pager motor" or "coin vibration motor" or "vibrating motor", but somehow I always end up with precisionmicrodrives.com.