Any good tool shop will have something, or Graingers. The threaded rod, nuts and washers I picked up from Tacoma screw because it was handy at the time. I bought fine thread heat treated, don't remember the exact grade, but it wasn't the usual all-thread.
That picture is the hollywood version of what I have, 30 tonner with a hollow rod, I usually put the butt up against whatever and let the nut and washer go up against the black ring there on the rod. Mine has a bit over 2" of stroke. Do you have a hand or air powered porta power pump?