You can find at major grocery chains like Whole Foods, Walmart, and Trader Joe's . In a typical store, check the International/Mediterranean aisle first; if it's not there, look near the nut butters (peanut and almond butter) or in the Natural/Health food section . Tahini Product Review & Guide
When shopping, it is important to distinguish between (100% ground sesame) and tahini sauce (paste thinned with lemon, garlic, and water). Most "tahini" in jars is pure paste meant to be used as a base. The Best Tahini You Can Buy at the Store (or Online)