I an fortunate to not have problems with squirrels. I farm chestnuts commercially and some people have big problems with them. A article a year or two in a nut grower publication indicated that the Kania trap proved the most effective and several individuals seem to really praise it. I provides a quick and silent death, perhaps very suitable for an urban location. You can check it out at
Squirrel traps, mink traps, rat traps, and other small pest traps
Good luck!