Try 'n buy parts for just about any other older bike. Harleys are like old Chevys. There are tons of used parts, or suppliers for replacement parts.
Try that with your Duck.
Ain't no problem. There's quite an aftermarket for Italian bikes. Heck! I don't have any problems finding bits for my old Guzzi. Not that it ever needs any. ;-)
The only parts you might have trouble finding are those with skulls or nekkid wimmin etched onto 'em.