The only thing I can suggest is to get an engineering company, or someone with a lathe to make up some rivits. If they copy the heads for one end you could then do the other end by hand using a suitably shaped rivit forming dolly.
I think I would find some bolts and do the front hub to match the rear. If you got replacement hubs from Skyway they had long screws and nyloc nuts to refit them anyway.