This is the only used one that I know of https://portland.craigslist.org/mlt/...412527108.html
Manual/CNC lathes are pretty rare. I thought about converting my 1340 to CNC and still keep full manual capability with instant switchover. Basically overlay the CNC over the manual. But I dropped the idea after I got a CNC lathe.
As far as cost, it depends on the degree of sophistication you want. It could be a few hundred to several thousand.