"Advanced Search", as shipped, would of course search through all the products. It sounds like your Retail Locator is still searching the product tables, rather than your retailers table(s). Do you not yet have the retailer table(s)? With no keywords, and still looking at product information, I wouldn't be surprised if Advanced Search matched everything. I think you need to do a little more thinking about the subject, and get some more code and data in place, before you ask for help.
Most stores which offer a "Find your nearest store" locator function carry the same goods in all stores. Do your stores carry different goods? I suppose that it is possible that your site is an umbrella for a number of related, but not identical, brick and mortar physical stores. A visitor would want to find the nearest store which carries the particular goods they're looking for. The first thing would be to geolocate your potential customer, either through their IP address, or asking for a Postal Code (ZIP Code in US). Depending on how geographically dispersed your stores are, you might use something like Google Maps' geolocation to get a latitude/longitude, and from there, calculate the shortest "as the crow flies" distance from the customer to a suitable store. For stores in the same city, you might want to get a more precise customer location, and calculate street routes for shortest distance. Keep in mind that a potential customer might be reluctant to give their street address, so don't push the issue. Don't forget to actually show a map, rather than just showing an address, and show several nearest matching stores, not just the one you think is closest. A customer might find it more convenient to visit a more distant store that is close to their workplace, for example.
Assuming your stores carry different goods, you could use products, manufacturers, etc. to narrow down the list of stores, and then find the closest store(s). Are the stores different enough to make this effort worthwhile? What do you intend to do if the potential customer wants some goods found only in one store, and other goods found only in another store? Can stores ship goods to each other so the customer only has to pick up in one place? They would appreciate that service.