This idea is orginally my dad's. He carries a black lunch box, decorated with marine core emblems and other pins he likes. He is super organized and come with this great organizer for a daily bag. Below is how I used this idea in my big black purse. Now, this dosen's need to be used 100% of the time, and of course, you can make smaller versions for smaller purses..I will attempt a smaller version myself as a project soon.
OK so all this is, is a large box, and several smaller boxes fit into the large box like a puzzle. Then you just organize your items. Sometimes things are a little longer then they need to be, either consider buying something smaller or rethink the size of your bag.
I have in my bag, eye glass cleaner and cloths, coin purse, check book, cell phone, makeup bag (this is on the ouside of the large box on the side.) Hand wipes,pens, goodies powder, tylonel, perfume, nail file,brush, and sunglass clip ons. Your bag may need to be a bit bigger. Though I don't to carry one as often anymore, I will soon make a ultimate diaper list for babies and toddlers.