Well I have a idea...not my own...this was back in the 80's in a country where such things are legal. I knew a rather heavy set fellow. He wore a chain around his neck, not much different than one that might have a cross or some such thing on it...in his case he put a 22 bore brush on the end of it. Now its been too many decades for me to remember for sure, but it was either a 22 freedom arms mini revolver, or a 22 double barrelled darenger, and he inserted the brush into the barrel, so the pistol hung under his shirt, he could just reach under his shirt to draw it. The shape was to indistinct to identify through the shirt.

Now you ofcourse don't mean a firearm, so you would have to modify this idea to work with what you have in mind.

I suppose you could use a money belt and put some essentials in there : a couple of $10 bills, a lighter (or matches), a small Victorinox Swiss knife... Can be tucked under your shirt and is invisible. That way if you were separated from your purse, you'd still have some basics.

I've got one of these from MEC - http://www.mec.ca/product/5001-813/onsight-money-belt/?q=money%2Bbelt

I have a plain black wallet/case for my iPhone 4.. in it I carry a coupla cards, some cash, my phone (of course), a credit card sized charger cable/led torch/battery pack, a few 1st aid supplies eg band aids n swabs and I can also fit a swisscard tool or wallet ninja in there.

the case is about the size of a small clutch purse, if a lady carries a handbag they have lots of options in small edc stuff.

So I guess it depends on whether its a clutch purse, small handbag or larger bag.