Might I suggest a personal taser? You can buy direct now, and it sounds as if you prefer LTL solutions. If not, there is always the option of a stun stick, collapsable baton, or brass knuckles "paperweight". All can be purchased through Cheaper Than Dirt, I believe. Hope that helps.....
It is illegal to use pepper spray indoors with other people around in Chicago.
Chicago ordinance bans "dirks, daggers, and stilletos". I pretty much assume they will categorize any fixed blade in that category, especially any knives meant for 'thrusts'. But then again, I assume they would call my SOG Flash 1 a "switchblade", but I still carry that.
As far as the stun gun, yep, they require a FOID which is unattainable for out-of-staters (no matter how much Cook County sales tax I pay on my wife's shopping trips.)
I figure the combination of an assisted open knife, pepperspray, and a bright flashlight is about as safe as I can be and still be legal.
Stun guns are illegal to carry in Chicago. You must register them and notify police in advance to possess them.
It is illegal to use pepper spray indoors with other people around in Chicago.
Brass knuckles are illegal in Illinois. Batons are illegal in Illinois.
Knives, as already stated, must be 2 1/2" or less in Chicago.
I'd go with an OC fogger or foamer and a push knife of maximum size. I like the Urban Pal.