When you say "inmate version" do you mean the Poison Ivy in the Arkham City video game? If so, I'd definitely go for that one! You can always add body paint(some brands are: Ben Nye, Snazaroo, Kryolan, or Mehron they're all really good choices) and vines and leaves to make it stand out more. But I definitely think that it's one of the most under done Poison Ivy's, but it's still super recognizable.
Upcoming Conventions: Katsucon, Anime Detour, Wizard World Minneapolis, C2E2
Young Ana Amari- Overwatch
Taako Taaco- The Adventure Zone