Yeah, I thought it was pretty weird too. I don't even like Zathrian so either I have him break the curse just to get the "Good" end, or join the Werewolves because Werewolves [i]maaan[/i]. The only one time I sided with him to kill Witherfang was when I was specifically creating a Very Warden Warrior.

I'm pretty sure the Grey Warden Compound would have a few replicas or something in their armory. Can't promise that, but it's a possibility.