Try lookin in junk yards. I wonder if they may have been a factory option or something. Eh... I might be blowin' hot air, I was 7 when they stopped building first gens. All I know is before I bought my truck I had a line on a '93 dually I almost bought that had stainless running boards. They seemed to fit up pretty clean, as if they were vehicle specific. Anyway, if you find them on a rotted out gasser that was put in the graveyard for rust instead of wrecking, the stainless boards should still be clean. The truck I wanted was rotted pretty good but the boards looked used, but pretty clean considering.
Try one of these street truck shops. A lot of those low rider trucks have running boards. There's a shop like that around here called Ultimate Truck or something like that, they surprisingly had some stuff I couldn't find at the 4x4 shops or the diesel shops.