n re doing my 88gt, I wanted to freshen up the hinges as well. the little roller that engages the cam had worn out and the pins and bushings were shot. I started to look for good used ones, but I figured, why bother with more used parts, so.... I bought rodneys hinge rebuild kit.. high quality and wow did it work good. so from now on, that is going to be my way of fixing them.
check for any gm car made the same time as your fiero. gm used many parts from diff. models. fiero ,corvette , firebird ..all had same mirrors. ect..ect. hope this helps you out.