First of all you should NEVER pay to shop. When you do, you have been scammed.
There is a list of 200+ companies in the first post of the first thread of the Mystery Shopping Company Discussion section of this board. I understand that a few of these may be charging a fee these days--just disregard them and don't sign up. To find out more specifically who has shops in your area, sign up with Jobslinger.com (the free version, not the JobslingerPlus version) and then put in your zip and the radius you are willing to travel. Sign up with those companies that you see. Similarly there are a few companies that have shops with nationwide clients where you are likely to find work. These are Market Force (blue portal), Bare and Corporate Research International. These are not necessarily companies you will want to stay with in the long run, but they generally have shops in every city, town and rural area.