I did mine about a year ago. They're standard metric bearings available at any local bearing supplier. Replace them both with the modern sealed, permanently lubricated ones. Should be under $10 for the set:
All the 5 Brush I have rebuilt I have used the sealed bearings; armature and interior stay nice and clean. I'm even running one one my Feb. 29 Roadster which I drive a fair amount. If you need any parts, except armature, let me know.
Without going to the basement to confirm it, I think the bearing is a #204, which Bratton's and most all parts houses should have. I can buy them local at the bearing store.