Ok, the answer is fairly simple, but somewhat expensive.

There were only two manual transmissions offered with
the Fiero V6 cars, the Muncie-designed and built 4 speed
or the Getrag-designed and Muncie-built 5 speed. The
4 speed, referred to as the "Muncie" in the Fiero world,
was offered through the latter part of '86 production
year, and starting with the last few hundred of the '86
production cars the 5 speed (referred to as the "Getrag"
in the Fiero world) was phased in. No '86 or later V6
Fiero came with the 4 speed, though it's possible that
someone swapped one in after the fact. The Getrags were
fairly rare in Fieros so the cables are getting hard to
find and moderately expensive. The Muncie and Getrag
cables are not interchangeable at all, sadly.

The Fiero Store may carry replacements, and it wouldn't
hurt to check Rodney Dickman's site at
http://www.rodneydickman.com too.

There's a mall section in the forum at http://www.fiero.nl
it probably wouldn't hurt to check there also.

JazzMan