You are speaking of a vibrating alarm clock... correct?
Not something that will shake your bed enough to wake the dead and throw you out of it?
Okay okay, seriously though. Here you go...
You can buy them on Ebay or Amazon much cheaper if you're looking to save money. I prefer something like this as a "back up" at times because I'm a HEAVY sleeper ( Thanks Ambien ) and I toss and turn a lot.
Amazon.com - Silent Vibrating Personal Alarm Clock "Shake-N-Wake" - Travel Alarm Clocks It's nice because it attaches to your wrist like a watch so if you move a lot and sleep heavy, you're covered. Of course, that isn't nearly enough for most people on its own... and certainly not enough for me... Best buy also sells vibrating alarm clocks...
Sonic Alert Sonic Boom Alarm Clock Sa-Sbb500ss - Best Buy Those are some moderately priced ones for you, of course there are definitely better brands out there that have much better ratings and are a lot more successful... but these are ones that will get you by if that's all you're looking for.