carry a machete and openly dispay it, that'll work i reckon.....
seriously tho, if you getting worried about where you ride, either ride with someone who can handle themselves, or look for somewhere else to ride, cause even if you do carry a weapon of sorts it's more than likely to get taken off you before you can use it if you do get into trouble..personally i'm not into that kinda thing, if i don't feel safe i'll not ride in that particular place, and i'm a fairly well build guy who can handle himself..
generally i'd say you are just being paranoid tho...