Most knitting stores will carry crochet items, as will places like jo-ann fabrics and michaels. I would think places like meijer and k-mart would carry them too, but your best bet would be craft or knitting stores.
You can find a crochet hook just about anywhere that sells Yarn. Wal-Mart stores that have craft sections always have them. Also you can find them at craft stores such as; Joann Fabrics, Hancock Fabrics and Michaels. They usually carry them in the yarn section hanging up on the shelf.
Check at your local craft or hobby retailer. Crochet items remain popular and the handiwork is considered a great gift idea for the receipent. If you shop at flea markets, you may happen on a great price for tools and accessories too!
You can get them in the craft department at retails stores like Wal-Mart. But for a larger selection is it best to go to a crafts specialty retailer like Michaels Crafts.