Plants like ficus and umbrella plants (schefflera) are great climbing plants. Pothos (devil's ivy) are extremely hardy vines, these I like to hang from the top of the cage and let the vines grow downwards - not AS great to climb for a heavy chameleon but they can help fill in cover towards the top of the cage, and the big leaves are great to drink from.
These should be common enough to find in any good nursery, I would immagine.