Two budget ball bag patterns:
The first is a softball cover. We made some of these for a group of new ML shooters. This was a team and we wanted them to have a simple and inexpensive bag at the range rather than dropping them all over the place. My son and I were playing softball at the time and we had some dead balls looking for a new life. I also had copper tubing and a flare tool.
We got old softballs and cut the threads. Then took one of the 2 pieces and folded it against itself to make a bag shape. Then cut the thin strap at the top. From there you stitch from one side to the other. You can make a spout out of a flared piece of copper tubing; carve one or even turn a wooden spout in a lathe.
This will give you a basic concept for adapting with better leather later depending upon the size of your balls and how many you care to tote around.
The second is Mike's can pattern.
Mike Nesbitt uses a frozen Welches' Grape Juice can as a pattern and basically mirrors that with leather. This also work well. I have one that he made 15 years ago and it is still one of my favorites. This one is quite functional and you would not figure the pattern if you were not told.
I hope that either or both of these work for you.
YMHS,
CrackStock