Kong Stuff-A-Ball, Rhino Dinosaur bones, Kong Biscuit Balls, and tire toys like Mamoth Pet Paw Tracks Tire Biters might be good for Jasper. Have you tried stuffing his Kong with goodies? Go to http://www.kongcompany.com for stuffing recipes. Here's a couple links to good chewy toys.. you might want to just order online, I do a lot even though we have a Petsmart nearby, sometimes they don't have all of the stuff we want in stock.

Petsmart toys

Tire toy at Petco