Forum:Lilith's Specter Mod - Where Can You Get It?

Pretty straight forward question...where can you find a Specter Mod for Lilith? I have one without the ammo regen and I want to see if I can find one with ammo regen. I just don't have a clue where I got it in the first place. Is it quest only? I've never seen Crawmerax drop one with over 200 kills on him.