threaded rod with loop on end

No , but if you don't mind the lack of chrome (powdercoat it ?) it looks like something anyone with a welder and a hacksaw could make . Might have to buy the threaded knob unless you can cast plastic (or aluminum ...) .

I think I might be tempted to cut it out of aluminum. Drill it it and put in a Helicoil T.

Then you guys got me making all kinds of stuff these days that I used to freak out about trying to find.

I think the Trac Rac has some knobs like that. As to the square on top of the stud, just bend and weld. If you do not want to bend the stock, go to a truck spring maker. They bend the new U bolts all the time.