The only regular non-immigrant visa category that would conceivably allow working in a shop (no matter whether paid or not) would be H-2B for temporary non-agricultural workers. But that is a purely theoretical option, because it will only be issued if the U.S. Department of Labor finds that it is in the interest of the U.S. economy to let the particular work be done by foreign workers. The chances of this happening for ordinary retail work are nil.
A few other types of non-immigrant visas would allow such work incidentally to the main purpose of the visa, but they all depend on you being in extremely special situations (as one example, victim of human trafficking assisting law enforcement with investigation) or a spouse/child/dependent of the holder of certain other visas. Since you write nothing about such things, that is pretty much a non-starter too.
For completeness, getting an immigrant visa also seems to be impossible. You don't write that you have any qualifiying family to sponsor a family-based immigrant visa, and the employment-based immigrant categories are even farther removed from retail work than H-2B is. For many, a final (though unlikely) option would be to enter the diversity visa lottery and hope to get lucky, but if you're born in England, Wales, or Scotland you don't qualify for that, due to the large number of Brits who settle in the US by other routes.
In short, as the comment said:
Forget about it. There’s no visa for that kind of arrangement.