Those hubs and wheels look very like series landcover ones. The size – R15 is not something I am familiar with. What size tyres are mounted on the wheels?
The wheel construction (riveted) looks very familiar, as are the 5 studs. Although the hub and brake drum are separate in a landrover.
So I wonder if a series hub would fit? Otherwise can you get the two parts welded together again? Specialist job, I know, requiring annealing afterwards and it must run true, but cast iron can be welded.
Getting the wheel bearings off will be difficult but if the broken off part can be recovered then you might be able to get the seized bearings off with a grinder. I have done this in the past with a seized landrover hub. Took all weekend to do though. You might be able to get a stub axle to weld onto the actual axle.