I had the misfortune of buying one of the 'Vietnam Specials' here on eBay from an unsavoury crowd who operate in Queensland under the title of Vespa Heaven. Check them out, they have a website with their name and dot com after it and the site looks real professional. Well it turns out that it's a one man operation where he works out of his mum's garage taking advantage of poor suckers like me. Beware of sellers who act as in-between onsellers to the unsuspecting public, they are just buying in, thrown together junk with second rate paint jobs and old motors that barely last a few months. I imagine there are some genuine honest business people out there and I'm sure their feedback would support them, but be very careful as you may end up with a lemon like me. Make sure you pay with PayPal as that will be your only saviour should you get stiffed like I did.
The most important thing to remember is your personal safety. These scooters are around 40 years old and have mostly travelled millions of kilometers, so they need to have been rebuilt with that in mind and have structural sections replaced with remanufactured sections and not just some scrap metal from the salvage yard. Vespa scooters have the whole chassis as a stressed structure and NO frame at all! So if the body breaks you are in serious trouble. The front suspension is a single round tube, this needs to be ideally replaced with a new part as who knows what stresses it has been subjected to and the next one may very well break it. Think of airplane wings, the metal can crack and fail much like a piece of wire does if you bend it a few times. So be careful and good luck.