I had the side window of my (American-made Snugtop) canopy replaced by O'Brien Glass. They knew what to order.
I had made one temporarily out of 3mm smoked perspex. I had them cut it to height, then I used a saw & file to cut the curves, then I drilled appropriately for the hinges and locks and gas struts, and fitted my replacement - which was almost perfect (except it was completely flat, where the glass version is curved outwards slightly).
Is a smoked perspect option available to you? I got my perspex from a signmaker, but you can find similar in Bunnings.