Send or take it to Alan Noakes if the rest of the teeth are worn, and he can graft on a new sprocket ring. He can also sleeve the inner spigot where it fits onto the hub, if it is a sloppy fit. If the sprocket is good, apart from the broken tooth, you could get it repaired with weld, and then carefully grind/file it back into the correct shape.
Richard Blackburn at Scottparts sells them (cush hub) newly manufactured P/n: SF0003.
I bought one for my ’38 Flyer after buying the one for the later hub by mistake — still sitting there gloating at me —
But be warned, these sprockets have undersized bores to accommodate the wear induced by the original, this means you machine them to fit.
I have my old one which is not to bad really and could be shimmed to suit if necessary?
It depends how hard you intend to use the bike.
Just a thought, send me a pm if that would be of interest.