Responsive design is the answer ! But still then you should think about the actual user scenarios from customer point of view on a mobile device. It is not very likely that a customer will go into depth on your mobile site like he or she does on your actual website.
You should think about your mobile scenarios. Which scenarios are important to support when on the go, when being mobile? Customers want quick access to your contact information, see the location of your store, find a map or directions how to go to your store, see some promotions or short overview of your services, see the brands you sell, … Since they are already on the move, they will find out the details in the store itself. So the main goal for your mobile site is to facilitate getting there and having the most important information directly accessible.