Hi and welcome here.

Unfortunately, I searched on http://www.ticalc.org and http://www.nspirehq.com for a "topography" program for the Nspire CAS and it returned no results. In ticalc.org case, there aren't even any for other calculator models either. Are you sure it isn't a different name than topography that you mean? Otherwise, you could check that page, as it has several school programs on it and might have what you need under a different name:

http://nspirehq.com/nspire

unfortunately, the emulator that runs the TI-83+ on the Nspire is not released yet and won't be for a while, and since the Nspire CAS doesn't have the 84+ keypad, it is impossible right now to send 84 programs to it

Hopefully maybe someone know a link to such program for the Nspire. We have to keep in mind that few people bought TI-Nspires before because they lack any game programmming capabilities, and Ndless is very recent, so most people went with a TI-83+ or a TI-89, so this is why the selection of programs for it is still very small.

Yeah sorry I couldn't help