If you live outside New York and want your own set of the custom-colored, 4-card set of these topography cards, you're in luck! They are now available online at the MoMA Store site.
And to answer your question before you ask it, no, I haven't wrapped my brain around the fact that the listing for my cards exist in the same sales category as the Tim Burton, Andy Warhol, or Frank Lloyd Wright notecards. That's just a bit bigger than this noodle can handle. ;)