There's the Tex Yoda and other Tex keyboards -- I suppose if nothing else there's buying one of those keyboards and repurposing the TrackPoint and its PCB if necessary?
There's been some tries in that area, using basically the blackberry trackball.
https://i.redd.it/ddu76x8mwg221.jpg https://i.redd.it/ddu76x8mwg221.jpg