Within the past year I have seen the cover, certainly the belts, the alternator/flywheel and I think most of the hardware on Ebay. Problem is, you have to watch Ebay constantly so you can grab this stuff when it comes up.
If you are going to go this route, you need to do a worldwide search, and also search the foreign Ebay sites for those countries where there would be a high probability of someone offering this stuff (i.e. Italy, UK, Germany, the Netherlands, etc.); since someone might be offering these items just in that country and not offering them for sale to the rest of the world.
1982 Laverda 180 Jota, 1974 Laverda SFC, 2010 KTM Adventure 990, 1992 Ducati Superlight, 1993 Moto Guzzi Daytona 1000, 1983 Moto Morini 500 SEI V Sport
I think you should be able to get the parts quite easily, it may take some time perhaps for the correct parts to appear on the market, be it e-bay or the Morini Riders Club, but you will find them.
For the cover, alternator/flywheel - probably e-bay Italy, perhaps UK & France
For the Timing Belt - go to your local French Supplier of Industrial drives & bearings, should be be approx Euro 10 (or less). Use a recognised manufacturer such as Continental, Gates, etc etc
Don't know if you got my post in the wanted section so I thought I'de post here as well. I have all the parts you require for your bike. PM me at: andyroach@yahoo.com
Or if you are thinking of selling it PM me as well.
Regards
Andy