  Internal Diffusion Limited Aggregation (IDLA) is a model that describes the
growth of a random aggregate of particles from the inside out. Shellef proved
that IDLA processes on supercritical percolation clusters of integer-lattices
fill Euclidean balls, with high probability. In this article, we complete the
picture and prove a limit-shape theorem for IDLA on such percolation clusters,
by providing the corresponding upper bound.
  The technique to prove upper bounds is new and robust: it only requires the
existence of a "good" lower bound. Specifically, this way of proving upper
bounds on IDLA clusters is more suitable for random environments than previous
ways, since it does not harness harmonic measure estimates.
