This first link is to Emgo. They have mirors, and also 10mm to 8mm mirror adapters, so one can use the vast array of MC mirrors on modern Vespas! The adapters cost only $2.50 each, from your favorite MC/Scooter parts dealer...

http://www.emgo.com/catalogs/05_Filter_Mirror.pdf

This second link is to a UK firm that also has 10mm to 8mm adapters (about $11.00 USD, the pair).
They also have a selection of 8mm threaded scooter mirrors you can buy from them. Shipping mirrors from the UK they say takes a week (via airmail), and costs around $10.00 USD in postage.

http://goodbuys4u.co.uk/welcome_to_our_motorcycle_depart.htm