They should be available now and "They will reach their peak in September and October," according to the official M&Ms fact sheet on the product.
Their press sheet also said:
M&M’S® Razzberry Chocolate Candies are now in stores as a limited edition for only six weeks. They are offered in single 1.50 oz., 11.8 oz. and 18.6 oz. packaging for $.55, $2.96 and $4.39 SRP.I'm not sure how strongly they suggest that retail price of 55 cents for a single pack of M&Ms, it's been at least 10 years since I've seen them sold for that as a regular price (though three for a dollar sales aren't uncommon).
M&Ms tried special editions of their candies in gourmet flavors such as Cherry Almondine and Vanilla Crisp, which are sold at the official M&Ms World stores and Target.
Anyone see them? Try them? Like them?