If you're serious enough to have your own set of balls you'll find no better way of protecting them.
Peradon Snooker Ball Case
This case is the ideal way to transport and store a full-size set of snooker balls. Each ball is held firmly in place whilst protected from scratches, sunlight and anything else that could reduce the life-span of your balls.
The case has space for 25 balls, which is 3 more than you need for snooker, so you can also store a set of billiards balls in there.
Each case has combination locks and comes with instructions for setting these to a number of your choosing.