I own a couple of these and they work pretty well. I don't think they are made any more as we haven't had them in stock for a few years and I often see people inquiring about them in Halloween forums. If you do come across one they usually have a hefty price tag.
If you missed out don't fret. Here's a how-to to make your own similar contraption:
There are also detailed instructions on the website.
P.S. They also made a Christmas version that features a tree instead of the lightning bolt. If you come across one at a yard sale you might want to snag it.