A practical ball bag can reduce your loading time. I first saw this design used by Mark Baker in one of his videos. It's simple, compact, and allows the user to easily extract a single ball with only one hand. They are easily made using scraps of leather and no more than an awl, some saddle stitching needles, and some waxed linen thread.
For the longest time we bought ball bags shaped like turtles that included a wooden plug to keep the ball within. I found that when a leather thong we used to carry the bag, it started to hurt. If we put the bag inside our possible bag, it became difficult to remove due to its size, and still required two hands to remove a ball. I believe everybody started out carrying their balls with this style of bag, I purchased this bag at a rendezvous somewhere, and decided that because the two colors of leather would make it easier to explain how it was made. As you can see in this side view of the bag the main body of the bag is made from beige-colored suede, while the neck of the bag is reinforced with pieces of dark brown saddle leather. Notice that there are horizontal and vertical lines of stitching which I'll refer to later..
When viewed from the edge, you can see the sandwich effect created by the leather layers. What is not visible is that the vertical stitching on the neck goes through all four layers, while the horizontal stitching only attaches the brown saddle leather reinforcement with the beige inner bag. Now if I were creating this ball bag from scratch, I would start by cutting two identical suede bodies, and two pieces of brown saddle leather to reinforce the neck. See the top photo at the top of this post. Next glue a brown "neck" piece to a suede pouch body for side #1, and repeat for side #2. Now use a saddle stich on the horizontal stich lines to secure the neck reinforcements. Now repeat with the other side of the pouch. Leave some clearance for the circumferential stitching that will follow. Once this is done, the neck reinforcement will be firmly attached to the neck of the bag. Now align the two halves of your pouch and stich to two halves together.
When complete, you can squeeze the neck and the two halves will open just wide enough to allow a single ball to pass through the opening. This particular bag works well with the .490" round balls I normally use, but if I were to make on for .610" trade gun balls I might need to make another ball bag with a wider neck. With a little practice you'll be able to extract the pouch from your bag, and squeeze the neck to drop a single ball. It may take some practice, but once mastered, it is so much faster than trying to pull out the stopper for a turtle ball bag.