You can make a handle by using resin. There are probably two techniques:

1 – get some PVC pipe, about 1in diameter, block one end. Put the handle upright into the pipe and pour the epoxy resin in.
Once it dries, you should be able to peel the PVC away from the epoxy and you will be left with a handle.

2 – with either epoxy or even fibreglass, soak strips of cloth in the resin, then wrap it around the handle, be careful to exclude bubbles. It would be best of the still wet handle could be compressed somehow, but once its dry, you should be able to tidy it up. Do a search for micrata to get some ideas.

Alternatively you could make some handles and simply glue them to the tang. Try and rough up the tang as best you can.