As of August 2015, Amazon.com and ShopFoodEx.com sell rock salt. In addition, Walmart offers the salt at some of its local stores. These brands of rock salt are appropriate for making ice cream.
Amazon.com carries Rival rock salt. This product averages 4 stars on the retailer's five-star rating scale. Positive reviews say that the crystals are appropriately sized. However, some reviewers find that the salt is dirty.
ShopFoodEx.com and Walmart offer Morton rock salt. Directions recommend using this over ice to cool beverages quickly or to make ice cream. Homeowners are also able to use it for melting ice on sidewalks or driveways. However, the company warns that salt sometimes damages concrete.