I found that a Baseball (5-gal) Bucket with a padded seat lid makes for an excellent Troop level first-aid kit. It's easy to organize (you can get dividers from Home Depot/Lowes), and makes a convenient extra seat when needed. There's even room for larger items, like a blanket, permission slips and epi-pens, or, in our case, personal "girl-stuff" items. We painted a huge "+" on it, in glow-in-the-dark paint, so it is easy to find at night.
I also require each scout to have their own personal first-aid kit in their 10-essentials bag.
Granted... we don't bring it on backpack trips!