"what features do you need that the example doesn't have?"
How long, what diameter, what weight is it to carry? What budget is the limit? Why rack and pinion instead of screw thread and crank? What section size for the rack?
Are you able to take items apart to re-purpose them or do they have to be exact fit and ready to assemble with or without tools?
Is this for one unit or 100,000 units? Prototype or deliverable?
3D measurements - how precise does the action need to be? How sensitive to movement?
I'm looking in that picture and I see a custom extrusion for the support and another custom extrusion to hold the crank/knob assembly. Do you want just the tiny sliver of rack?
I have a couple of David White Stereo Realist cameras as well as some nicely made slide-bars for regular cameras. I also have a reasonably good projector and lenticular silver screen.