If you decide to search for 5 speed panda gearbox with cables you can also look for fiat uno gearbox, not only panda. I am not sure about the year but about 93 or 94 all unos with fire and ohv received cable mechanism.So 5 speed from uno 1000 or 1100 fire from arround 93-94 will fit, but it must "look like" the one you have, because simultaneously there were at least three types of gearboxes installed in unos with fire engine,{ probably all depended on where the car was assembled, Italy, Poland,Turkey or Brasil, cars from all four factories were sold simultaneously in Europe in mid 90s}do not buy anything without seeing the pictures of the gearbox

I have heard that early puntos had also this gearbox but haven't seen so can not confirm.
Ps:
There was also the third type of gear-change mechanism, a hybrid like, containing one rod and one cable, it was placed inside the cabin, in pandas from early 90's arround 92 to 95. I think it was connected to the newer type of gearbox,but never seen one live, only in the pictures. A missing link between rods and full cable mechanism maby?
general idea:

closeup near the frewall:
