A good supplier of all sorts of fasteners and clips, like body side molding clips, ground effects rivets and clips, plastic rivets and expander fasteners, aluminum rivets, christmas tree fasteners, rubber wellnuts for the rear spoiler, or almost anything you need to attach pieces to the Fiero can be found at Au-ve-co Products. When I reattached my spoiler to my current 85GT, Sage Glassworks provided wellnuts made by Auveco. They were exactly what was needed.
They have over 18,000 items in their catalog. Most can be viewed online. They sell only to retailers, but his will help you when going to the auto paint and body supply store, as most major brand stores are vendors for Auveco Products.
http://auveco.com