Payment Reminder Redirect and IPV6?

Just doing some research into IPV6 and I was wondering how I would accomplish the payment redirection I do currently on IPV4?

Right now I have a dstnat rule that redirects all TCP port 80 to the Mikrotik web proxy port of 8080. I then in the proxy redirect their page request to our local web server’s payment reminder HTML page. I also make sure to block all other traffic for those customers.

How would that even be possible in IPV6 on mikrotik as there is no NAT rules in the firewall?