You might want to ask the vet for a small bag of an alternate kidney diet food to use as treats thats the easiest way out.
This site has some treat recipes that might work out if you check the ingredients with the vet
http://fooddownunder.com/cgi-bin/search.cgi?q=treats
Ask about using Cheerios as treats or rice cakes or bits of vegetable if he liks carrots to chew.
Mini marshmallows might work too though they won't be great for his teeth.
This site has some home cooked meals recipes for dogs in renal failure too
http://www.2ndchance.info/renaldisease.htm
Also ask the vet if the brand food you use or another one has dog biscuits in a similar formula.
For example this site has a rice cookie it says is ok for dogs with kidney problems and says vets sell them and other places may also carry them
http://www.miraclecorp.com/stewartpet/
Hope this helps you!
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