I also have a windjammer fairing which had a cracked windshield.
Instead of trying to track down a replacement, I made one.
At Home Depot they have high impact Lucite. I bought a sheet along with a plastic jigsaw blade. At home, I took some craft paper and drew the outline of the windshield, then transferred the lines onto the lucite backing. A little trimming with the jigsaw and I had my windshield.
I placed the lucite on the fairing and clamped it down with some quick clamps, and drilled out the holes with metal bits.
2,500 miles later it's still in great shape with minimal scratching.