Try walking in the early morning or in the evening when it's cooler, and bring water with you (for you and your dog).
A lot of the high quality dog food aren't sold at
PetSmart or Walmart
, etc. Unfortunately, you would have to special order them, or find a small specialized pet store. The reason is that most of the top quality dog foods don't mass produce for large chain stores like PetSmart, Walmart, or a supermarkets, etc. They end up catering to small doggy boutiques.