Trademark in URL

I am trying to rank for the keyword "buy productname" and the domain "buyproductname.com" is available. However the merchant for the product that I am promoting will not allow the product name in the URL of my domain because it is a trademark.

If I create a genuine website on a completely different domain to promote the product (eg. myrandomblog.com) and then sign up with the merchant's affiliate program, is there any way that I can create another site on "buyproductname.com", rank that and then make it look as though sales are coming through the "myrandomblog.com" website? The reason I ask is that I think it would be a lot easier to rank "buyproductname.com" than any other URL.

Thanks for your help

I think you better find another product, without any brand/name restrictions in URL

Things like this have not been set in google regulations.
For example:

Keywords car

People who use banned buycar cargo

This will reduce the level of domain sales