Bburago has made a 1/24 diecast Saab 900 3-door model with rally graphics and Finnish company Stahlberg has made 1/12 (according to what I saw in the net) promotional model of the 5-door model ca. 1985. I believe I had one of these Stahlberg Saabs when I was a kid, but I don't think it was that large, more likely 1/24 - 1/20. However that was 20 years ago when I was 5yrs old so I may remember wrong... The model was made of softish plastic and was quite well detailed.
You can see 900 toys and models at
http://members.home.nl/bop5/models/900/models900.htm.
-Mikko