I am trying to visualize the crank.. I will describe two different cranks
one is a round shaft, solid, with a "Slot" in the end, not unlike the head of a screw if you look only at the end
The other is a tubular shaft with a pair of "notches" in the end opposite each other.
If you have the first. Like I had on my APACHE PUP.. Just go to a place that sells metal bar and rod stock.. Have them cut off a piece of the proper diamater and put a pair of 90 degree bends in it.
Take a grinder and grind a slot in the end (An angle grinder can usually be gotten with the proper size slicer)
Or bring it to me and I'll use my grinder to slot it.
If you have the other kind I can't help you easily but there are used-(Salvage hardware) places in our library here who may have the part
Finaly suggestion would be to contact the slide maker.