Atris has it, and kill her as often as you like, she never gives it back. Plus, the only way to get Master Robes is to kill a Master. If you desperately need a particular color, save a game before accessing the Duros' inventory, then just reload until you get what you want. In fact, Geriel the sick guy could also give you a power crystal. This means where you might find a lightsaber crystal (the Duros shopkeeper on Citadel Station, the sick man on Nar Shadaa), it's unpredictable what color it might be. Most of the stuff available in The Sith Lords is random. How do you find the silver/red/cyan/whatever lightsaber crystal? I figured, since no walkthroughs are up yet, I'd answer some questions that bring people here.
No, these are hits from people looking for tips on KotOR 2. Now, these aren't due to anything I've written or any witty observations I might have had. Over the last few weeks, I've had an explosion of hits for this little blog.