i made one for my sister, all i used was some chilli oil, lots of chilli pepper, lime and lemon juice, salt and vinegar and some aniseed powder. Mix it togther and put it into a perfume atomiser (large plastic one from Muji)
Fill a camera film container with fine ground black or white pepper and keep it in your jacket pocket. This would incapacitate any human or canine assailants when thrown in their direction at a reasonably close range. If the law got curious, then you lurrrrve it on your Bic Macs, but McD's don't keep pepper unfortunately, kind officer.