Have you tried Cuz's?

http://www.petsmart.com/global/produ...usText=Cuz&N=2


I've got a German Shepherd and he has destroyed numerous toys and household objects (walls, doors, dressers) because of his chewing habits. I got him two Cuz's and he hasn't destroyed them yet. They are really fun to play fetch with too because they bounce like crazy
German Shepherds can be very destructive dogs (Sometimes they are fondly known as German Shredders ) and the Cuz is a very popular toy in the GSD world. Trav chews on his daily and hasn't even managed to puncture it. We've had one of his for a few months now and its still in one piece. As you can see http://petoftheday.com/talk/showthread.php?t=118688 it goes through a lot

At the store they run for around $10 for the large ones, but it looks like you can get them online for $6.