A report on the Collect-U2 list has the Argentinian Vertigo DVD being NTSC (not that it'll be easy to find). Also, I believe the Japanese version is slated to be released; that ought to be NTSC, too.
Someone can feel free to correct me.
In any case, though, your point still generally stands. DVD singles are never cheap enough, and we always have to check format, region coding, etc. Argh!