I don't think anyone will be picky, particularly when they know it's an international submission. The requirement is just to standardize things, so people aren't printing on all kinds of unusual sizes. I say don't go to extra effort to track down the paper.
Also, so few places are requiring paper submissions these days, and I know some of the ones that do will make an exception for people mailing submissions overseas. That might be something to ask about first before spending the postage!