While helping a friend look for a Scarabeo like mine, I came across a site that was new to me. (I did a search and didn't find any posts about it - sorry if I'm late to the party and everyone knows about it)

It does a nationwide search of craigslist, ebay, etc for scooters .....

Example of Piaggio search:
http://scooterfinds.com/piaggio/for-sale/

or Vespa:
http://scooterfinds.com/vespa/for-sale/

I like how you can mouse over the scooters on the map to see which ones are near you. I used to use crazedlist to search multiple craigslist sites - but that can get you blacklisted so I use it with caution. But this site is pretty cool!
(I am not affiliated in any way with this site - I just found it and thought it was pretty cool for finding used scooters)