The Hallock's that are being sold for around $300-$400+ are not an easy project. I bought one and have more than 40 hours in it to make it fit the cowl, mount to the door pillars, and weld the two halves together. I had to narrow my cowl about an inch to make it fit. I think it would be easier to make one of laminated 1/4 inch aluminum plate.
A fellow Hamber is working on it. He is making progress and I'm sure he'll see this post and pm you...
HAMB member dave at ROADSTERS.COM is selling some awesum windshields, I don't know that they fit A's and I don't know what they sell for. I hope I was no help haha