So you wanna make a pokeball? Check out mine here:http://joshkreza.tumblr.com/
Its pretty easy.
1.get a clear plastic acrylic ball of your size and choice. I got mine from hobby lobby for about a buck a piece. you may have to cut a small hoop off as these were meant to be Christmas bulbs.
2.Paint the two halves the corresponding colors with spray paint. Obviously red and white for normal.
3. to give the poke ball weight, stuff it with one of those shopping bags you get from target or walmart.
4. glue together, with the bag inside.(superglue or contact cement works best.)
5. cut two circles and a strip of foam to form the black band. I actually used rubber tape because I had so much of it lying around. I'm still working on a good way to cut the circles cleanly.
and you are done. hope this helps you.
(btw this is a tutorial derrived from an image that I found while observing the boards. I did not make the tutorial nor am i taking credit for it.)