Ok, I think that this would work for you. I carry one similar to my medical calls(from my car to usually the patients house)Now when I am responding to a patient in remote areas I use a medical back pack.Just for ease of carry.

I do use a MAXPEDITION back pack for everyday carry for my lunch, extra cloths, water bottle, FAK, even my laptop or mp3 player depending how long a day is going to be. In other words I live out of my backpack on a daily basis (Is this a Man Purse? )