Well it would depend on what chalk you're currently using, what method of application (ie loose or balls) and why you don't like it, then someone can advise what might help you get the most out of your non-coke powder problem!
I use loose chalk (I always find that I never get enough chalk with a chalk ball) and it seems to do a very good job of lumping together into 1cm sized lumps that I can't crush with my fingers,(I think I have bleaustone loose chalk) but it only seems to lump up when it gets cold, other than that it is actually very good!
Personally I do something similar, I use a refillable chalk sock (costs just a couple of quid online) that breaks down the powder lumps as you use it along with some loose chalk surroung it in the bag. Works fine for me and is much cheaper than buying balls every few weeks.
J
Paul
J