Hardware stores sell that epoxy repair stuff that's like a long tootsie roll with half hardener and half resin.

You kneed it together and it starts to kick. You cold fill it with that and in 15 minutes it starts to stiffen up and you can shape it with your fingers.
I've used it and it hardens like stone and you sand it later or add a little more. Very easy to work with to create shapes.

I agree with Nick, some enamel paint over it and it's done.