Thanks, I will get some measurements later.It's not a cone, it's a spacer, also serving a cover for the cartridge.
"Non-drive-side spacer" would be my guess.
You might find other brands will fit -
if you post inner (10mm?) And outer diameter at the bearing end, and length required, I can grub through my axle parts drawers?
Nothing is branded at this level, so once it's off a broken hub, it's pretty anonymous.