My 91 and my 94 have the same switch, but the dash was changed in 95, and then again in 97, and it doesn´t look like the older switch would work in your car. Not sure about the 3g switch tho. I´m pretty sure you need a defroster switch from a 95 or 96. Won´t matter if it´s an LX or GT because the switch is the same.
You could try to rebuild the switch. That´s what I did. It was pretty easy. Mine is a 93 though. It would blow the fuse every time I turned it on. I took it apart and just cleaned out all the soot, and now it is perfect again. There is a little spring that alternates between holning the button in and not holding it in. It might have fallen loose. If any part is broken in there, though, you probably can´t fix it.
Yeah Nuke, unlike every other car I´ve owned, the scort has a simple on/off switch for the defrost. I mean the switch doesn´t leave it on for a while and then automatically turn it off. Should be easy to wire it to your other switch once you get at it.