We use two 5-gallon buckets with these easy spin on/off lids from Home Depot : http://www.homedepot.com/p/Leaktite-Screw-Top-Black-Lid-for-5-Gal-Pail-Pack-of-3-209299/203923741 .
We are fortunate enough to pull a utility trailer with plenty of room to carry our stuff and these two buckets. One bucket hold a hose and all its connectors and the other bucket holds one additional hose and the water hose we use to clean out the sewer hose with (we do not want to use the same hose that we use for drinking water).
If we did not have the trailer, I would use a front mount on the truck and one of those flat carriers. The lids will not come off in the wind.
The added benefit of these buckets is that they make good seats or tables if needed.