There’s absolutly no mention of any lightman in the 1981 script that I could find, or the revised '82 script either. If it were to occur anywhere, it’d be somewhere in this small section. Although not written anywhere, I’d imagine the Lightman would be a guide through the darker areas of the Palace.
9 INT DUNGEON CORRIDOR
One of Jabba’s Gamorrean guards marches Artoo and Threepio down a dank, shadowy passageway lined with holding cells. The cries of unspeakable creatures bounce off the cold stone walls. Occasionally a repulsive arm or tentacle grabs through the bars at the hapless droids. Artoo beeps pitifully.