There are several ways to deal with cross-site follow-selling on Amazon:

Contact the follower and ask him to stop following. You can contact the follower through the contact information on the Amazon platform or outside the site, and ask him to stop following and remove the infringing products.

Apply for a product patent. If your product is unique, innovative and practical, you can consider applying for a product patent. This will effectively prevent other sellers from following your products.

Join the Amazon anti-follow-selling program. Amazon provides an anti-follow-selling program to protect the interests of brands and sellers while ensuring that consumers purchase authentic products.

Submit an infringement complaint to the Amazon platform. If the follower is infringing your copyright or trademark rights, you can submit an infringement complaint to the Amazon platform and provide relevant evidence.

Please note that each method has its advantages and limitations. When choosing a handling method, please weigh it according to the specific situation. If you need more help, please consult a professional or lawyer.