I've got a front fender extender for sale off a '93. It's a black, thick plastic piece that extends the front fender lower on the back end. It's part 8 in the following schematic. I've also got one bolt and nut so you'll have to get another set for it to install it.
http://www.bikebandit.com/houseofmotorcycles/suzuki-motorcycle-gs500ep-1993/o/m6053 (http://www.bikebandit.com/houseofmotorcycles/suzuki-motorcycle-gs500ep-1993/o/m6053)