You don't tell us what the exact task is, but you could look at a 'running down tool'. The version with rollers bearings would be known as a roller box, usually mounted on a capstan, but I see no reason why it couldn't be held in a toolpost with a bit of fiddling about to set it up. see page 202 in **LINK**
Other daft idea, mount a travelling steady on the cross slide via the slots,lock the cross slide and swing the topslide round 90 degrees and use that to put on the cut.
I think I've only ever use a travelling steady a handful of times in nearly 50 years messing about with model engineering, so taking a bit of time bodging for a one off is not wasted