Dave miller has em but they’re a little pricey I think. Also the one Karen posted can work but it needs the correct bolt pattern drilled and from what I remember the bore is wrong size but it is the correct sprocket
Do what ole4 said. Get an nos Salisbury and use a 20 series comet. Late 73 speedways actually used the Salisbury 330. Not sure if your is 72 or 73 but all you have to do is bent a little section if it’s a 72. Here’s a photo of a stock setup on a late 73. The bent section is stock for mid 73 up.