A simple walking stick. I have used one to fend off dogs with no blows at all. Simply having a stick will keep many dogs at bay. It would give time to spray the thing for instance. Another thing I have done several times is to simply stoop down and pick up a rock. If there are no rocks then pretend to pick one up, they can't tell. Most country dogs have been rocked a time or two and didn't like it. I am not saying it will work for every person every time, but I will tell you that every time I have done it the dog acted like I had a force field around me.
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer