I thought I should resurrect this old post, incase the original poster ever checks back.
I wonder if you have found a windscreen? I wanted to pass on what I discovered when I looked into this topic a little. I spent some time looking at the Healey 100/3000 images to understand the windscreen/and softtop/hardtop.
I was surprised when you/AH Spares mention the BN1 screen. My 3000 screen looks much more like the BN7 screen in its construction.
When I was putting the softtop/hood on my car on my car I bought a part from AH spares (AH191) which was a finisher turns out, I did not need it, but I learned several things, mostly I learned it was perfect match to the length and curvature of the top of my 3000 screen. So it confirmed my expectation that the screen is similar to BN7.
Also when I fitted my screen I initially had several inches of gap ( perhaps up to 3 )at the centre of the windscreen and I had cut a plywood support/former from the under scuttle, pushing in the sides in a little and create a new support which brought the body up to meet the windscreen. You may find that the body structure might need similar "adjustment"
Given my experiences I would strongly suggest you look to a BN7 screen as the starting point. I can't guarantee it will fit but I would bet money that it could be made to fit!
Also apart from AH spares you can also look at Moss. It looks like the frames and pillars will be expensive and hard to find, the cheap option would be Aero screens going for the 100S style car. With the bumper delete this would save you a fortune on the chrome
Regards Jon