Did you get your James wheel bearings sorted, I'm working on a '34 KTS Velo, it uses cups and cones on the front wheel, the cones are 26 TPIx1/2 inch, not 20TPI, for 5/16 balls and the cups are 1 1/2 inch OD x 11/16 deep but these could be narrowed by grinding down the front edge. Velo specialists Grove Classics keep new ones. I can send photos if it helps.
I haven’t managed to find any yet, so many thanks for the message. If you could send some pictures over it would be most appreciated. The dimensions sound very similar to the rear hub of the James, which is also shot on my bike. It should be reasonably easy to mill down the cone if it is marginally too big.