Are you confusing calcium chloride (snowmelt) with magnesium chloride (also snowmelt)? It is extremely unlikely that you'll find pure mag chloride snowmelt in Colorado.
If you come to the next club meeting I may have a few pounds of 94-97% CaCl for trade. I use Excel snowmelt from Sam's, which is only available during winter months. A single 5 gallon bucket is only about $17, and will make about 54 gallons of calcium solution.
If you still want MgCl6(H2O), it's available on the Internet. Your problem will be in acquiring small amounts.