Runaway 2 year old (and he don't care!!)

I have a almost 3 in October boy who runs on sweetness, cuteness, and jet fuel! He has a great outlook on people and has never had a negative experience with anyone. This is good on one hand, but it also has created a very trusting child who assumes everyone is nice and there is nothing out there to harm him. When we are out he will NOT stay with me. Every time I ask him before we go in somewhere, "Are you going to stay near mommy?" "YES!" "Are you going to run off?" "NO!" Go into store and BAM he's gone to whatever section he desires (usually to look at the watches). He's a fast little booger and twice complete strangers had to point in what direction he went in because he truly outran me. This scares me to death. Is my only alternative to ride it out until he will mind better, and strap him in the cart? To him, "chase," is the best game on the planet. The more irritated I get the funnier he thinks it is.