Seems like every Target carries Clif Bloks, and almost always, they’re the cheapest. And my tiny little neighborhood market also carries Clif Bloks - Clif is really good at getting people to carry their products.
Honestly though, I’d probably look more for Red Vines, a loaf of bread, a jar of peanut butter and some tin foil if I left my nutrition behind on race day. (Target also carries KT tape and quite a selection of running gear, shockingly enough.)
I don’t know what a “Clif Blok” is, but I can bet they are way overpriced.