Give the heavy duty black kongs a whirl - stuffing/freezing them might help too.
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The only thing is that they get a little harder to screw together when you wash them. A quick squirt of cooking spray usually does the trick I like them because you can pack them as full as you want, and adjust how tightly you screw them together depending on how easily your dog might give up on them.
For a heavy duty chewer I'd order the biggest ones they make, pack them pretty tightly and freeze the night before.
In the past when camping at FW we've packed them with a mix of our dogs' kibble and a little plain yogurt and frozen the night before. If you google "recipes for kong stuffing" you'll get all kinds of good ideas. Just make sure whatever you use is something you know your sensitive tummy pup will be ok with.
These days when the dogs are home while I'm at work, I just put a smear of peanut butter in them - just enough to distract them for a while until I sneak out the door.
Whichever you go with, give them a try at home first to see if they're going to last/work.
When we leave our pups in the camper they each get a stuffie, and then we put on the TV and leave either the fan or a/c going for white noise. Shades down and all is well.
Good luck!