I use one of the Cliff Beast boxes for my smallie flies(poppers, mice and the like fit fine) on the water. I have a file system at home of Plano 3700 boxes to keep everything organized and I can just restock when need be.

I have seen people make their own version of my box though. Pencil cases (from Hobby Lobby?) or pistol cases with a little foam glued in will work great.