I have emailed Italjet on their website and I am awaiting a response. The engine was a  "bultaco" based engine.  I believe that alot of the parts are available from various distributors i.e. cables, shocks, brake shoes can be relined, hard plastic like fenders. Engines have a Nickasil chrome bore and somebody may make a piston?  
My bike is pretty much original, although I don't have the headlight option anymore. I will post something if I find out anything. 
Robert