Union generators still exist, I'm told, but trying to find a U.S. shop that orders it could be challenging. Try Harris Cyclery or a shop that recycles old bikes.

But unless you are looking for a historical replica, I'd suggest you visit Peter White's website and look at his bottle generators. The cheapest Dymotec 6 generator will have much less resistance than that old bottle of yours, and the Luimotec headlight also uses good optics and a halogen bulb, so it might be worthed to spend extra for the new headlight as well.