It is something you can only get at an Abiogenisis; that or, perhaps this Halloween. One other option would be to ask someone for the spelldata of the zombie set, but this is frowned upon by many players as it's seen as "cheating", and you'd have to learn how to properly use it without deleting important game-play files in the process.

So in short, I'd just wait for the Twin Gods to cast it on you. There's so many "zombie"s running around anyhow--we have a lot of lovely sets what with the Mardi Gras sets still here! Unless they're staying, but I haven't heard news on that, or it may be old.

/rant