I inherited from my grandfather a brace for drilling. The top knob is fine but the cylinder handle (I don't know it's name) is missing. I can't seem to find a replacement part for it. Any suggestions?

It's a great tool I use all the time especially for driving screws. I get great control so I don't strip screw heads like I do with the electric drill.

I think this might be a tool where buying new is cheaper than the replacement part.