Yes, there are plenty of Pokemon balls already on Thingiverse - but none of them seems to me to print quickly enough. So I designed a very simple ball with a button which is printed separately - so I could print it in different colors.
I printed a bunch of balls and played "analogous Pokemon-Go" with the kids - more like easter egg hunting. No electronic devices, outside, fun :-)
The balls were than exchanged with low-poly Pokemon models - hidden in plastic cups as incubators :-)