I've decided to go ahead and make a replacement screw with a sliding
handle (like a vise handle), but also with a hex on top "just in case."
This is a 14x40 lathe and there is plenty of clearance. Its not a
giant, but its decent size and there is room to work on it.

I have on 1144 stressproof, 4140QT, and cold rolled on hand. I have no
issue using the 1144 or the cold rolled, but I can't pick up 4140(QT
TGP) at a reasonable price locally. I hate to "burn it up" so to speak
on personal projects. Given the ease with which 1144 machines I am
concerned about shearing off threads on an 1144 bolt, but I have no
issue using it because I can just go get some more if I need it. The
cold rolled is really to soft IMO for making bolts.

I know the 4140 is tough as heck, and would make the most durable bolt,
but I hate to use it up if I don't have to.

(This isn't all I am doing, and its not "critical.")