Bulk paper orders of every kind: https://www.xpedx.com/

Or, depending on the type of work you are doing, you can go direct to the factory. I do a ton of print work in my job as a creative director, and I love French Papers, Crane Lettra is great (it's all cotton, which is puffy and wonderful). These may not be good for laser work though.

You can hit up the guys at public-letterpress.com, they specialize in doing high end letterpress and laser work. That's who I'm going to ask about this sort of thing once I place the order for my laser.