Just hoping someone might know im missing the front chain sprocket off this 250cc its it has a keyway and shaft has thread on end and thats about as much as i know
Have you tried contacting Hitchcocks about this ?
They would be your best hope.
If they have a prewar parts list for an S, it will have a part number, and they can see if they have some, or the specs for having some made. And the nut to hold it on.
If they don't, engineering/agricultural shops keep sprocket blanks.
You'd have to measure the taper angle - they come often in std sizes, not as random as you'd think, and measure the chain size, and have something suitable made up. Agricultural places do this all the time, the price of original farming parts can be absolute murder, but cheap to make up.
The depth of the taper is the only tricky part, and the keyway depth.
Finding an old sprocket someplace would be rather helpful - and the sprockets for the larger cc models are interchangeable to some extent, so maybe the smaller ones are too ?