List 25 from the rosters your buyers’ industry already publishes

Association member lists, state licence lookups, or a Google Maps search by category and postcode, where the review count is a free size estimate. A licensed business is real and operating, and almost nobody else is writing to it from that list. Maps gives the phone number too: an owner who runs the business from a phone answers a call, not an email. In the UK a sole trader counts as an individual, who must agree before you email them, so call or write instead.