Another vote for Magic Chalk. In fact, I can confidently say this is my favorite chalk, and has been so for a number of years.
Once in a while, I'll stray away from Magic Chalk (as I did just recently), but I always come back. Recently, I used Blue Diamond for a spell, wearing a cube of it down to the nub. After I got done with the Blue Diamond, I can confidently say I like the Magic Chalk better. It just goes on quicker, smoother, with better coverage. I guess I'm a spoiled brat.
The price is worth it, too. It's approximately the same price as Blue Diamond (a couple dollars a cube), but not astronomically "out of the ball park" like Kamui chalk is.
I'd like to mention that I've personally done business with eBay seller "billarstudio" and although the somewhat broken English may scare you, I want to let everyone know that every single transaction was flawless. He deals in hard-to-get pool and billiards-related items, and what he writes in the ads / pictures he includes / prices, are right on the money. He also responds quickly to any communications, answering questions as best he can.
I'm well-stocked in Magic Chalk at the moment, but the instant I get low -- and as in the past -- I hit up "billarstudio" for more.
As far as manufacturers, there might be a few:
http://www.alibaba.com/manufacturers/russian-magic-pool-chalk-manufacturer.html
Though it seems like you would have to make really big purchases since these are the manufacturers.
Be careful with those searches, because many vendors are using what's called "template" pages that absorb the key words you type in, and reflect them back to you such that their page comes up in search engines as "hits." Notice how your EXACT search phrase came up, word for word, in their page description? That's a dead-ringer "template" page. Many very aggressive vendors are using these, as a form of "reverse spam" -- meaning, they absorb your search terms exactly, and come up as false hits on a search. Many Chinese vendors are doing this, as a means of cracking additional business in the U.S.
Just FYI,
-Sean