A colorful water pistol filled with Ammonia shot at the face of a mugger works well. Just make sure you have one that does not leak.
In the camera bag the pressurized can of wasp/hornet insecticide can be used against a mugger. Grab, trip it and nail them. The stuff shoots 20-30 feet and will mark them with the smell even as they are trying to see with the stuff in the face and/or eyes. Keep it where you can reach into the camera bag easily to get it for use.
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