Not sure if I would agree on the very great shape, but...
For the handle you want to use something that avoids yielding easily (bending and taking a set), commonly 4140 bar stock is a good solution. Although 1144 and the like would save you some $ and unless you REALLY are using the vise you shouldn't have an issue. The bigger problem and I will have to go measure as I don't remember off the top of my head, is if the hole is of a common bar stock size, for some reason I want to say they are not. Meaning it would have to be turned the entire length for a best fit. You would also want to check to see if the hole is actually round and not egged. You other big obstacle is going to be how to attach the ends. The three common methods of peening (need a torch and jig, welding (need a welder) and threading (needs to be threaded before hand) or a combination of them each require some specific tools. So.... what tools do you have.