I'm currently role-playing my Dwemer noble, and I want to get the Dwarven Crossbow. The Dwemer, being unconcerned about other people's problems and/or their lives at all, wouldn't make sense to join the Dawnguard. It doesn't concern my characters cause, and I was wondering if there is a way to get it without joining them? Is there a way to steal it?

Thanks in advance

Nope. Its among the final parts in the crossbow series of quests. So unless you're on PC, you are out luck.