I searched for a new fiberglass bellypan, mostly on Ebay. There are a few, but i didn't like the shape. And the price.
So I turned to good old Aliexpress, and found a modern looking belly pan - I mean "engine spoiler" for the BMW F900R/XR. I ordered a set, knowing that maybe I cannot fit it, and have to throw it into the trash. But, for the price (US$ 42) it worth a try. After a lof of cutting and welding converted the BMW specific mounting hardware to fit the FZS, and also had to cut out some plastic on the left to avoid a cooling hose. Here's the result: