According to the legend, Dragon Scale Legs are unobtainable - meaning you cannot get them from any creature or quest. From what I heard you can get these only if you deserve them and there's only 3 legs in all of the Tibian Land! I don't think there's any recent updates on whom owns the legs because I've been constantly been asking around.
In 2004 a player by the name of Lostboy obtained them for being a Goodboy. He apparently owned a key that used to open and close all the house doors in Thais. He was basically a landlord whom rented out apartments for the middle class. We're unsure of the year in which Pskonejott got his legs but apparrently he was also a goodboy and reported bugs for his. Lastly on July 26th 2007 a player named Abertt got his legs for purchasing premium - He was the 100,000th player to purchase premium!
A fun little fact is there's an item called Chocolatey Dragon Scale Legs , you can't even eat this! But you can easily obtain it by killing Pinata Dragons which happen during Tibia's Anniversary, January 5 through January 31. You can also obtain Tatty Dragon Scales Legs during Tibia's Anniversary event if Vigintia Island is open!
Source: TibiaWiki