My two fight over a chew toy made by Nylabone...it's for "power chewers" like Emma!
Here's a link to one.
http://www.petedge.com/Durable-Denta...ne-TF22101.pro
They LOVE it! It seems kind of big and heavy for them, but they don't have any problem carrying it around, so I don't worry! I'd rather it be too large than too small and worry about them choking on it!