You'll find more references under "Syncmaster 20 GLsi" rather than the model number. There are several driver sites with drivers that purport to be compatible, with user reviews of the drivers ranging from very good to useless. Some suggested the 3Ne driver would work.
As SRS mentions above it's not listed in the product support sections of Samsung's own site (it was the first place I looked), but there is a contact email on the site. You could e-mail them and ask them if they can supply you with a driver. (I don't know how helpful a large company would be, but I've had excellent replies from smaller companies when I've e-mailed them about problems).