Welcome to the forum. You are actually asking your question where it will get fairly little response as merchandising is a bit different than mystery shopping.
Without reliable transportation you will have a great deal of problems finding enough reasonable work to keep you busy. There is a company that routinely has $5 phone shops to funeral homes, there are other companies that have occasional phone shops. You will need to register with a number of companies to see what you can find offered.
Here is the basic problem, however. I have transportation but would just as soon stay at home in my jammies making phone calls rather than burning gas if the shop pays reasonably for the work involved. I have nationwide phone service with no long distance charges. So you will be competing with me and with any other shoppers throughout the country who want those shops.