You could take a normal hood and aquaseal/neoprene cement the bib to the underside of the jacket. You would need to trim the bib so it sits flat without bunches. I think a triangle cut in the bib, with the point going up to the top of the hood, would help it lay seamlessly along the collar of the jacket.
Sewing alone would not prevent water intrusion, so you might as well not sew it solely. If you want two pieces of neoprene to stay put together, you've got to glue it. Sewing with wetsuit manufacturing adds extra structure, keeping the aquaseal from pulling apart. Sewing alone means you're eventually going to tear your neoprene apart along the stitching.
For what's it worth, Neoprene cement is more forgiving for beginners. Follow the directions and when it looks dry, press your pieces together. If you mess up, you have a few seconds leeway to pull apart and do a quick recoat and press together again. After it's set, paint along the edges and press and smooth to make a seal that will catch the edges if you're overlaying neoprene on neoprene, rather than connecting two piece's at the edge.
