If you're wanting every VM to be NAT'd behind a different public IP address, you may be able to use a VPN service to accomplish this. Some VPN services even have port forwarding features. If you're wanting each VM to be reachable from the internet with it's own dedicated public IP address, this may not be a wise thing to do from a security perspective. But if you really want to do this latter option, you are going to need to purchase public IP addresses from your ISP and then have a router configured to route incoming and outgoing traffic. The VMs would likely need to be on a bridged NIC so they can talk directly to the router. I suppose it might be possible to get your host machine to be the router, but that would be even less desirable from a security standpoint. Maybe you can tell us a bit more about what you are trying to accomplish from the big picture, because there might be a different way to do it.
