As I got a flyscreen for the GBS Zero GT (wide body), and it fitted very well on my scuttle, I'm pretty sure that their windscreen kit (available from
Kit Spares) also fits the Haynes (the GBS zero GT's dimensions are very close to the Haynes', if not exactly the same)
Problem is the scuttle profile. I think, if I had to go the GBS route, I would order the glass separately to a glass manufacturer/supplier, and have it cut to the exact profile of my scuttle, and use the rest of the kit from GBS to fit it.
Please keep us informed of your progress on that matter, I'm very interested, as I'm also considering that (but need to save money first
)