My 2 cents:
Buy your own water tight box & make your own. IMHO, the majority of pre-made kits have a LOT of stuff you won't need/use. You end up with higher quality gear & a better kit in the end.
Things i have never seen in pre-made Kits, that I use all the time in my family:
Waterproof band-aids
eye flush cup
high quality tweezers
mole skin
waterproof tape
high quality snake bite kit---never used & hope i never have to.
high quality finger nail clippers
waterproof matches/lighter/fire starter & dry storage container for them
poison ivy oil remover & treatment
blood clot
For my home kit, i bought the largest R-maid food container at w-mart & filled it myself. It has saved the day many, many times. A couple things, every time you go there & before long you have a custom made, real world first aid kit. Sometimes, it is wise to put things in there that you have never used & don't know how to use because someone else may know how to use it & that may save a life.