only thing i can think of is either the dealer itself, or an auto body shop could probably contact Smart or somebody and find the mixture of the paint based on the color and whip some up themselves.
I contacted one of the West Coast dealers who was selling touch up paints online. He informed me that UPS had recently changed their 'hazardeous materials' shipping regulations and that it could no longer be shipped. I guess they're afraid that such a huge amount of paint could explode or some such thing ...
Check with your dealer the next time you're there - or better yet, call since not all of them carry everything. My closest smart doesn't carry any touch up paints.