Listing branded products without copyright

EDIT: Title should say trademark not copyright.

Hi all, I have a question which I can’t seem to find an answer to on this board and Amazon support isn’t being particularly helpful. Here is my situation:

– We are a UK based limited company that works with manufacturers overseas which product unique, branded products for us. The brand name is different to our limited company name
– We’re currently working on registering a trademark for the brand name, however this process can take months
– In the meantime, we would still like to be able to list the product on Amazon.

The issue is that they are asking for proof that we are licensed to sell the brand. I’ve tried creating a letter of affiliation which was essentially from our limited company saying that we are authorised to sell this brand, however Amazon didn’t accept this (as expected).

Has anyone had experience on dealing with this situation? I’m not sure what else I can try other than waiting for the copyright however it would be a shame to not list anything for a few more months.

TLDR: How do I go about listing branded products without a trademark we get custom made for us? Is it possible to prove that we’re licensed sellers?

Appreciate your help!