The Fiero antenna is a fixed-mount wire that is common to many GM vehicles of the same vintage. The antenna base is threaded making it simple to remove/install. Replacement antennas for all years can be found at auto parts stores under the "Champ" brand, part number 9-1518. Used antennas are readily available in salvage yards.
Electric antennas can be mounted to the Fiero with a little work. An example is at www.fierosails.com/ElectricAntenna.html