1. Your First Approach: If you approach a merchant as a sales agent, you will become: "another one of those Sales Rep, who wants to sell me something".  You will most likely receive a NO answer or they will hang-up on you. 

On your first contact, introduce yourself as a customer.  Ask them if they have a website you can visit to check out their products, prices and/or store information.  If they tell you they don't have one, show them how surprised you are.

Let them feel as they did not fulfill a customer's need, and this service should be provided to you.  Note that most merchants already understand the need to have a website, you just need to reinforce it, and make them feel this is something they need to act upon quickly.  If you succeed to do that, you now became the rescuer.  THEY NEED YOU.

2. Your Second Approach: Now that they feel you did not come primarily to sell them something, but to use their services and products, introduce yourself.  You have something they need.

In brief, you need to:
Assess the Situation
Identify the Need
Create the Urgency
Offer the Solution