Looking for a safe and convenient way to store and transport the black powder used for ejection charges, I found the Traditions Performance Firearms Muzzleloader Composite Tubular Flask with valve (black) at Amazon.com. It cost less than $15 and arrived in two days since I have an Amazon prime membership.
The flask is made of a hard, black plastic. It has a high-quality feel to it. The top screws off and it holds about six ounces of black powder. The flask has a button that you press that opens a valve allowing you to dispense just the amount of powder you need.
I usually use Newtons 3rd ejection cannisters or I make ejection charges using plastic wrap. In either case, the Traditions Performance Flask will make the process it easier and safer.