So I found this pattern on Ravelry and set to work making one.
I used the basic idea of this pattern and figured it out for the size of Logan's Pikachu. Then I decided that I wanted to add only one zipper instead of 2. So I basically made the top and bottom half and the button. Then I attached it all together with the zipper in the middle.
It worked pretty well.
Of course, it's not as round without a Pokemon inside, but it still resembles a Pokeball.
Now if only Logan could get Pikachu to stay inside the ball.
The little guy keeps trying to escape!
(link to my Pokeball Project on Ravelry)