Large paper needed

Can anyone suggest where I might be able to source large sheets of paper with which to fold models at an origami convention? A0 or larger, ideally. A "roll-end" would be perfect.

A professional print shop. My printer buys very large sheets and cut them down for me into. They come in some odd size, not sure if its A0 but I know it was bigger than A2. I used to buy card not paper but its worth asking any print shop, especially if you only want a few sheets. Not sure what weight you would need but I expect you would know that.