I still run the electric types but so far, I'm still running an original armature and field. I think there is still at least one person that can work on the little armatures such as the horns have. I run the Heinze HA-C1 types since they have a stamped steel base. The ones with the zinc die cast bases like the Owens Dyneto haven't survived as well so they can be problematic to restore. I have a few spares to scavenge parts from when needed.
Some new parts are made for the electric ones but it's generally just replacements for the plastic and zinc items that like to break. The little electrical wire plugs made from bakelite are available and fit most electrics. Some of the rubber mounting parts are also available. It basically just depends on which unit the owner has, as to how difficult it is to restore.