The no solicitation signs on many businesses serves 2 purposes. One is to keep people from coming into their business and stealing customers $, the other is to keep potential clients off the backs of management. The first thing I would do is place a phone call and ask to speak with a manager. Find out how their store goes about purchasing goods to sell. Many companies do not purchase locally but rather at the regional or corporate level. If you find the store manager is involved with purchasing try to arrange a meeting to discuss your product and how it would fit in with what the store has to offer.
It s called selling.
