Baymule
Herd Master
Great idea!Going out on a limb here - esp if the food is costly and you can't get samples to see if he will even EAT it.
There has got to be a homemade diet for this that you can cook up and freeze in sandwich bags. Many years ago one of my dogs had kidney issues, she was a working dog and the "experts" would not take that into consideration - they'd only work within the lines of what a pet dog would need. Spent $ for a consult, got basically nowhere - and ended up working things out on my own. On their diet she was "dead dog walking", on mine she was happy and still got to work.
~maybe you can find something you can cook up.