I made my truck's FAK using a zippered rubber worm/lure case. The one I used was made by Tackle Logic and is even FAK red. It has 8 heavy duty, zip lock type bags on binder rings in the zippered case. I have everything broken down to separate needs in the bags: various pain relief tablets; assorted bandaids; triple antibiotic, burn gel, sting relief; larger bandages; wound closure; EMT shears and light surgical needs; gloves and prep wipes; etc...

It's very convenient and easy. Just unzip and flip through to what you need, everything is visible. I think I paid $9 at a local Academy, but something similar and in a variety of sizes can be found in most fishing supply depts.