Risk of buying a diamond from a conflict region is rather small: about 4%.
There are several ways to be more certain. For example, you can buy a diamond from Canada (Tundra, Ekati, Polar bear, etc.). Rand (one of the sightholders) diamonds are coming with certificate stated non conflict origin of their diamonds.
I'm sure there are other ways also.
Btw, some of the famost diamonds aren't conflict free at all.
Buy an estate piece with an old cut diamond and you will not be buying one from any conflict. Or, buy from a vendor who can give you a known source for the stone sucvh as has been suggested. Canada for colorless, Australia for brown and pink. You might even consider man made diamonds in fancy colors that finding their way to retail consumers, too.
When will we start cutting EightStar in Canada? Labor is 1.6 times cheaper here."
There are very few EightStar cutters and the training is long and specialized. Even if you could convince them to move to Canada, they would still have to be paid for their very unique and masterful skills.
Oh, and who are you referring to when you write, "we"?