You can find aged balsamic at stores that specialize in olive oil and vinegar, they often have them on tap and let you sample to see which you like best. Check your area to see what is local to your area. Williams Sonoma also sells aged balsamic, as do other more specialized kitchen stores. It's difficult to find aged balsamic in a regular grocery store. I like 18 or 25-year balsamic vinegar. Note, this kind of vinegar shouldn't be used as a cooking ingredient, but where it can shine, like as a finishing touch to a dish, served fresh with cheese or berries, or creamy desserts.