Took the 2-piece pin to the local Tru Value hardware store.
There is a correct name for what I'll describe, but I'll be damned if I can remember it... hawser pin?? Anyway, found it in the selections from those stacks of flat drawers holding all the fasteners and stuff.
Bought a "pin" of the correct diameter and the friction-held "cotter pin" like thing that goes thru a hole in the other end of the pin.
This pin has a flat head like a nail, passes thru the upper and lowers, and is held solid by the cotter-pin like "thing". Worked like a champ!!