I would say it is a generic part used for nearly a century, and a local auto parts place should have something in either Dorman brand, or Help brand.
As long as the specs are for the same axle thread diameter, and if it has the tang, it should work.
here is one on the Dorman site, for 3/4" if that is what you have. Click where it says specifications, for the thread size. It comes with the nut. They have other ones to look at, under "front wheel bearing washer"
http://www.dormanproducts.com/p-6861-3049931.aspx?origin=keywordI will have a 1929 front bearing apart today, if you need a measurement, as I would think it would be the same size