I actually sell and ship a lot of live oak, magnolia, and bay leaves. The main reason people like them is that they are durable. Most leaves with toxins would not affect an animal unless they consume the leaf and I believe that toxins begin to break down when the leaves dry.

If you want to maintain a local look to the tank, you might consider mountain laurel or rhododendron leaves, which are thick and probably would hold up well in a damp viv environment.

I'd be happy to sell you some leaves, but I only sell in bulk (1 cf (7.5 gal) or more) and I'm sure that if you only need a small quantity, something local would work. The deciduous oaks would work as well, but if the substrate is too wet, decayed leaves get messy and for species that don't like their feet wet all the time, this wouldn't be the best set up.