Safe T Sorb isn't actually a cat litter. It's similar. Holds up much longer, as does Turface.
Home Depot, depending upon location, does occasionally have similar products.
Best bet for finding STS is to check out the retailers I mentioned above. If you have a location close to you, it'll cost about $5 for 40 pounds. If not, it's about $10ish for 40 pounds - including shipping.