The most direct and effective way is to log in to official website. Generally, there will be the sales staff and contact information of the manufacturer. Some manufacturers will also have an interface to apply for an agent, just fill it in directly, and then someone will contact you. If you don't have both, you can call its service number (usually starting with 400 or 800, which is definitely there), and you can definitely find someone under normal circumstances.
You can find the contact information of the manufacturer's sales from the local distributor or the insiders who operate the product, but remember not to go to the local agency for the product. Of course, there are also some industries that are not sensitive to the increase in the number of agents, such as opening specialty stores. In this case, you can also find a local agent.
Of course, if you manage a certain kind of products well in the local area, some manufacturers will contact you actively.