Ugh, I'm so sorry this happened to you. Harness is definitely a good idea.
Others can tell me I'm being mad for suggesting this (and maybe I am), but would it be possible to talk to the owners of Boa on your own without Hunter by your side? Their reaction (kicking Hunter) is understandable if they were acting out of fear - I'm not saying it was right, mind you, just "understandble". Now tensions seem ramped up not only between Hunter and their dog, but between the humans. That could make further encounters even uglier. Maybe if you made the good-will gesture to apologise for what was an accident, explain that you are buying a harness for Hunter so that the same thing doesn't happen again, but also ask that if the dogs ever do come in contact again, not to resort to kicking as you all know at this point that any encounter is going to be a lot of scary noise but no actual harm.
Again, this may be a terrible idea. But it also may reduce your stress and keep them from spreading nasty gossip about Hunter that doesn't help anyone. What do others think?