You can buy the commercial loaders, they are pretty much waterproof unless you go swimming.
You can go to craft stores and buy plastic bead tubes with lids.
Or stop at the bank and get penny or nickel rollers load with powder and tape shut.
Or do what some guys like me do. roll paper cartridges.
Tie the ball or bullet inside or separate. Carry these in a tube if need be or a small plastic box.
There's several websites on rollong cartridges or you can pm me and I will explain it.
Another option for close in work while doing your rounds carry a revolver. If you load it with paper cartridges you can leave it loaded almost indefinitely. If you can resist the urge to just shoot it!
Have fun shooting