Hi Morten
You can order roll paper from any of the manufacturers through a local distributer. I buy rolls in all different sizes and emulsions for particular jobs, It is very economical to cut from a larger master roll.
Warning , some vendors will sell 30ft rolls as opposed to 100ft rolls, get the 100ft as there is terrible curve in the smaller offerings.
I would suggest going onto the paper manufacturers websites to find out dealers in your area and ordering that way.
good luck