An outfit called Windwave distribute FSA in the UK. Look them up then Email or call them. I’m not that familiar with FSA stuff. It may be a standard crown race for all 1.5” Orbit headsets, but don’t bank on it!
If it’s a separate crown race then the spec might be etched in underneath. IME convention (is there such a thing in headset standards?) is internal angle followed by external, i.e. 36° crown race Find your headset on the FSA website and look at the service doc