Meet up to film a viral video
 

I am looking for a large group of Segway enthusiasts, fans, and owners to meet up in a flashmob sort of way to make a viral video.

This video will be used to promote a Hollywood sequel that is currently shooting in Las Vegas and due out next spring.

Are there any Segway organizations that still exist today where I can communicate to a large amount of people about organizing a meet up?

Not too many large organizations.
I would check with the polo folks. Most likely the largest organized group of seggers around.
You may also check with local dealers, and see what lists they have.
Of course, you should also post here, but it will give you a more global and less local reach than you are likely looking for...

Good luck. Keep us posted.

I agree with Karl, Segway Polo is one of the last major Segway organisations around.