On the Tetra website, they list these uses:
Agricultural Nutrients
Animal Feed
Dust Control
Fluoride Removal
Food Processing
Gas Drying
Ice and Snow Melting
Mining
Oil and Gas Drilling
Ready Mix Concrete Acceleration
Road Base Stabilization
Tire Weighting
Suppliers for these industries would be the best place to look - maybe food service supply or agriculture supply. I've also heard of Tetra showing up in some pool stores.