I don't know what parts you're after or where you live but an easy to place to start looking is on eBay Italia. There is always a steady stream of Zigolo stuff coming up and nowadays its no great drama buying stuff from another country using PayPal.
Even if you don't buy much it will show you what parts are easy to get and what is a little trickier.
Zigolos don't seem to be that collectable in Italy at the moment. The smaller Moto Guzzi Cardellino seems to be more fashionable so get in quick before the Italians realise they are ignoring a real fun little bike.
Cheers,
