The Franco-American center in Manchester may help connect you to other fluent speakers.

Unfortunately, the usage of French has been dwindling year by year in New England, even in places like Madawaska. I have heard the French speaking population went up in the past few years in Portland, Maine, due to refugees and immigration from French speaking countries.

Your best bet is joining a club for French speakers. Also, there's always the Quebecois or Acadien tourists during that season. There seems to be a steady stream of French speaking tourists in Salem, MA.