If the castor is w/in certain limits, any towbar will back a toad around a corner. Don't need no special X bar to do that.
What a bunch of BS. Plain to see why the guy went broke. And plain to see why there is no such thing being made, and probably never was.
And yes, back in the 60s, some vehicles would not steer on a towbar. We just tied the steering in the center position, and it worked great. A little tire scrubbing in the corners, but it never showed on tread wear.
And even now, if you tie/lock the steering wheel in center, you can back up any toad forever.