Wow, that's a challenge.
I have heard of people paying for high-end boarding for a few months, but the kind that keeps the dog from being stuck in a kennel is very expensive. Do you have a trainer who you like and trust, who might board the dog? If you have a vet school in your area, I've also heard that vet students sometimes do stuff like this (for pay), to make a little money while they're in school -- you can call and ask the school to post a notice for you.
Sadly, I know lots of dogs that landed in shelters because of military orders, and their owners couldn't rehome them in time. In fact, the shelters around bases tend to be full of dogs like this. That tells you how hard it is to find temporary fosters! My best friend's GSD was one of those dogs. My male also came to me through similar circumstances, as his owner had to relocate to Africa for his job in the oil services business -- and the dog was left at a city shelter. Give yourself lots of time -- it may take several months to find a good solution!