From the Roving Trader Tracker homepage, directory and events directory you can search for nearby traders or events:

You can enter a search term (to find a business by name, description or the products/services they offer), enter a date (e.g. to search where traders are today / this week / this month) and a location + radius to find traders near your location. Use the geolocation button  to search for businesses around your current location (subject to device compatibility, accuracy may vary).