Because these smaller Italian-manufactured machines were pretty much disregarded by the Italians themselves until reasonably recently, there isn't a comprehensive spares service or parts remanufacture like there is for say big Guzzis or bevel Ducatis. It's a case of trawling Ebay and the small ads websites for sometimes months, hoping the desired bits may turn up.
I haven't got months, and anyway it's August, and Italy is closed for business. So, hacksaw and file in hand, I made the required bracket myself. Much as I'd like to, I don't have access to lathes or metalworking equipment, but for a bracket, you don't need much. A bit of patience and a steady hand - I was always pretty good at making Airfix Stuka kits when I was a kid. Forty minutes later it was done and on the bike.
Satisfaction guaranteed and problem sorted.